fix typo(s)

Replace all instances of mkdirRecurse with ensureDir ...

All usages actually want to ensure the directory is present,
and don't care about having a separation between existence check
and creation.

Merge pull request #2526 from dlang/add_path_workflow ...

Fix add-path based development workflow

Fix version match rules for add-path based packages.

Move foreign code from global scope to dub.internal. ...

Avoids conflicting with the actual dub packages when working with dub as a library. Also, even if just by convention, it ensures that dependent code doesn't rely on this code as a public API.

Unify reading and writing files under a single API ...

This removes the range API and instead uses Appender,
while using a limited and centralized set of functions
to read/write from files.
The end goal is to permit dependency injection,
which is a pre-requisite to extending the test-suite.

PackageManager: Load packages lazily on dub build ...

A problem of the current design of dub is that all locations are scanned,
regardless of what action is being performed, often multiple times.
With this change, a regular `dub build` on a project with all dependencies
resolved will no longer loads all available package, which can substantially
speed up development.

Document PackageManager.getBestPackage, deprecate Dependency overload ...

The Dependency overload is not needed, as calling getBestPackage
with an SCM / path dependency does not make sense.

Deprecate `PackageManager.refresh(true)`, only expose `refresh()` ...

It is not actually used, as all call sites but two use false as an argument.
The two calls using true are inside a constructor, meaning there will be no
pre-existing packages, so whether true or false is passed will have
the same effect / result.

Do not use Phobos' sumtype, use dyaml's versioned one ...

So that we can compile with older versions of the frontend,
currently v2.097 instead of v2.098.

Fix zip symlink problem.

Fix package scanning order. ...

Packages registered using add-path need to come before cached packages.

PackMan: Provide an overload of storeFetchedPackage that doesn't expose Location ...

This way we keep the internals of PackageManager within the PackageManager,
instead of having external classes be aware of the paths we use.

PackageManager: Only iterate on internal fromPath array, not everything ...

getOrLoadPackage is only used for path-based dependencies,
which are only stored in m_internal.fromPath.
We can thus reduce the iteration by only using fromPath.
If someone had a path-based dependency that pointed to a version-based package,
it would lead to this package being loaded twice, but that's not really a concern,
as it would not lead to problem either.

Remove PlacementLocation information from Dub.fetch ...

Let it rely solely on the PackageManager instead.

PackMan: Deprecate overload leaking location path ...

Currently, a lot of the internals of the PackageManager are leaking.
The getPackage overload accepting both a version and a NativePath
is an example of such a leak, and looking at the usage sites
show that things can be simplified by taking a PlacementLocation,
which is a higher level representation of the path.

Move PackageManager.getPackagePath to Location ...

It is more suited as a Location method, as it returns a path based on PackagePath.
This also allows us to reduce the leak of information about Location
happening in dub.

Deprecate PackageManager.completeSearchPath ...

It is no longer used within the PackageManager and leaks quite a bit of the internals,
instead users should have functionalities exposed via the PackageManager's API.

Deprecate an unused PackageManager.getPackage ovrld ...

This overload is not used anywhere in `dub`, and its use case is not clear.
Path where packages are stored should ideally be only known to `PackageManager`,
and the API should expose `PlacementLocation` instead of bare `NativePath`.
With this in mind, this overload doesn't fit the picture.

Deprecate PackageManager.getFirstPackage ...

This function returns the 'first' package, which is very arbitrary.
Instead, always return the highest matching package for stable results.

PackageManager: Simplify removeLocalPackage by using algorithm ...

Instead of doing (potentially) multiple append operations of two slices,
just do a filter + array which is much easier to read and prove correct.

PackageManager: Remove m_disableDefaultSearchPath, use array instead ...

The boolean is redundant, as the array will always be null / empty
if it's true, and have 3 entries otherwise.

Trivial: Improve PackageManager.m_repositories documentation

Remove PackageManager deprecations from v1.20.0 ...

Those deprecations have been introduced in v1.20.0,
so if we follow the same 10 releases policy as DMD,
we are good to have them removed in the next release.
Deprecated in 48a26db

PackageManager: Make internal scope have the priority, remove m_temporaryPackages ...

Before, `m_internal.fromPath` was unused, and `m_internal.localPackages` was only
used for the bare mode search paths, while a similar array of packages named
`m_temporaryPackages` was used for `Repository` / `NativePath` dependencies.

In both cases, this array should have priority over the other scopes,
so we can just remove the duplication and swap the iteration order.

PackageManager: Move the scanning logic to Location, segment per Location ...

Before this change, all packages were surprisingly stored in m_internal.localPackages,
which itself is a new addition to replace an array of 'Package'.
This means that even though we had an architecture that looks like it segmented
things per repository / location, it actually didn't,
and things worked solely based on the order packages were added it
(and the fact we did a linear search).

PackageManager.Location: Split packages registered locally and read from path ...

A Location, having a default search path (the package path),
and some extra search path, optionally, previously stored
all of them in the same array. However, this creates problems,
as we want to move to lazy load the packages in the default
search path, while we can't lazy load packages in non-default ones.

Trivial: Fix some style issues

PackageManager: Simplify logic around refreshing packages ...

Passing an empty array will lead to the same behavior
as using a boolean, so we can remove the parameter.

Trivial: Rename refresh_existing_packages parameter to refresh