fix typo(s)

Merge remote-tracking branch 'upstream/stable' into merge_stable

reduce dependency on the working directory ...

Improves library API usage and bugs with the build generator

Fix various DDOC warnings

Use a central build cache for all build artifacts ...

Currently the central build cache is not configurable,
but as most build artifacts end up in `~/.dub/packages/` anyway,
this will be a positive change for users.

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.

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.

Make the test runner code more readable ...

Using manifest constant and a single format call,
the code will be more readable than piecemeal additions.

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.

Use getPackage instead of getBestPackage for resolved dependencies ...

getBestPackage is intended to find the highest local version matching a range.
Due to this, it has to eagerly load packages and iterate through them.
However, when loading a resolved dependency, we have an exact Version,
which is simply wrapped in a VersionRange, so we can call getPackage instead.

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.

Project: Only print warning about mismatching dependency specs for versions ...

When using path-based dependency or repository dependencies,
we shouldn't need to validate those as they always match.

Fix #2450 - issue1474 testcase is broken on Windows

Use configy library to parse dub.json file ...

This will provide a vastly superior UX to the users:
- They will be warned about typos;
- The type information provided will be more accurate and always include file/line infos
  (e.g. no more 'Invalid SemVer versions');
- We can expose a better recipe struct to library users on the long run,
  by separating the actual data DUB uses from what it reads;
- We can be more descriptive about errors / intent, for example by using `SetInfo`;

Trivial: Remove always-true condition ...

isExactVersion will never return true if repository.empty returns false.

add $DPATH environment variable for file locations (#2281) ...

* error out on unknown environment variables

* add env + config for package + settings locations

fix #229

* adjust to review, extend $DPATH test

* review round 2

PackageManager.getBestPackage: Introduce Version[Range] overloads

Project: Use Dependency.visit instead of if/else

improve some output coloring ...

See #2347

Integrate Configy colored output with dub's

settings/selections: Only warn on unknown keys, add changelog ...

This will give users the time to adapt, without erroring right away.

Keep logging functionality out of the public API as requested in https://github.com/dlang/dub/pull/2124#issuecomment-813016939.

New logging module - initial functionality ...

The new module replaces dub.internal.vibecompat.core.log by using the
same function names, but implementing colored output and the left
fixed-width tag. Overloaded functions are provided to output colored
text.

Still missing initLogging() and non-TTY stdout/stderr detection

use json.get directly instead of casting ...

see https://github.com/dlang/dub/pull/2321/files#r928547114

Use Configy to read dub.selections.json

Move PlacementLocation from project to PackageManager ...

PlacementLocation define which local path is used for storing packages.
It has nothing to do with project (it's not even used there),
and should be contained inside PackageManager, even if currently
quite a few details are leaking all over the place.

Trivial: Streamline code when package not found in project ...

Instead of checking the same condition three times,
just do it one, and make it more obvious we're actually
handling different kind of Dependency.

Fix missing deserialization of fileVersion from dub.selections.json ...

A regression in master, which can lead to `dub upgrade` generating an
invalid dub.selections.json (with fileVersion = 0).

Deprecate duplicated JSON serialization for Dependency