Minor: Align dub.recipe.selection style with dub.recipe.packagerecipe ...

During review of the PR that switched PackageRecipe parsing to use Configy,
WebFreak pointed out that having an internal, private structure used for
parsing YAML field was preferable to having it at module level.
This aligns the names and the approach used with the one in PackageRecipe.

Trivial: Fix typo in documentation

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

Dub: Use UpgradeOptions.dryRun instead of printUpgradesOnly ...

The latter is said to be deprecated, and this is the only usage.

Trivial: Reduce noise and allocation while reading local-packages.json

Trivial: Improve dub.packagemanager : Location documentation

Deprecate overrides: local-overrides.json, add-override, remove-override ...

As explained in the changelog, overrides were a solution to a system
with version-only dependencies, which is long gone.

Trivial: Improve 'dub list' description

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.

PackageManager: Move scanPackageFolder to Location ...

A simple move for now to keep it simple,
the breach of abstraction will be resolved in a latter commit.

PackageManager.scanPackageFolder: Do some cosmetic fixes

Fix #2450 - issue1474 testcase is broken on Windows

Fixes #2452 - Accept non-existing file in `sourceFiles`

fixes #2448 - Accept sourceFiles without module declaration

Posix: Add default SONAME/install_name for dynamic libraries ...

Setting it to the filename (ELF) or `@rpath/<file name>` (Mach-O).

This seems to be required in order to use the libraries copied to
the output directory of dependees - either by setting the
LD_LIBRARY_PATH env var when starting the executable, or baking a
RUNPATH into the executable (e.g., via `patchelf --set-rpath` for
deployment).

Otherwise the loader tries to load the library from the original
location specified in the linking cmdline, which is some
`<path to dep pkg>/.dub/…` path (and apparently potentially
relative, and thus even more brittle). For ELF, I would assume
that all SONAME + DT_NEEDED entries (of executable + all .so libs)
would need to be post-processed to enable loading the libs from the
executable's directory (well, any non-original location).

update version to v1.29.2-beta.1

PackageManager: Move class' extra searchPath/Package to an internal location ...

Those fields have been aggregated in Location and them being in `PackageManager`
stands out as a double duty (the `PackageManager` is both a `Location`
and act as a `Location` manager). By using a `Location` for them we can
start to streamline the code.

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: Convert some spaces to tabs

Trivial: Remove always-true condition ...

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

Trivial: Remove test about the internals of Dependency ...

Now that Dependency is a proper SumType, this can never happen.

Trivial: Remove redundant comparison ...

optional and default_ are indeed checked by opEquals.

Trivial: Correct code to use match's value instead of property ...

This code was accidentally working as it was calling the path property,
essentially entering another match on the SumType.

Trivial: Remove dead import

Remove 'unknown' version ...

It was never used.

Dependency: Deprecate path/repository setters ...

There is no real use case for changing a dependency in place,
instead we better let the user overwrite the dependency itself.

initPackage: Use VersionRange instead of string

Merge pull request #2435 from Geod24/getBestPackage-redundancy ...

Remove redundant lookup when searching for a tool

Signed-off-by: Nicholas Wilson <thewilsonator@users.noreply.github.com>
Merged-on-behalf-of: Nicholas Wilson <thewilsonator@users.noreply.github.com>