Hoist imports and remove versioning in FilesystemPackageSupplier ...

Hoisting imports to have them all in the same place.
Also remove a version statement, as the client code should not
care if vibe-d is being used and just import the internal module.

Remove PackageName alias this to toString ...

The alias this was originally added to make the transition
less painful, however due to an overload resolution bug,
it makes it harder at the moment, as thje compiler prefers
calling the deprecated `string` overloads over the
`in PackageName` ones. So remove it and a few hacks along
the way.

Adapt PackageSuppliers to PackageName API ...

Since we recently did a semi-breaking change to PackageSuppliers,
now is the time to do it again (they will be in the same release).
Again the same logic applies: it's only a breaking change for those
inheriting from PackageSupplier, not those calling it,
and there is likely not a lot of people doing either out there.

packagesuppliers/filesystem.d: Only look for versions of package_id ...

When looking for versions of a package don't include any files that
aren't versions of the queried package.

If a directory contains the files botan-1.zip and botan-math-2.zip
the current implementation would report both 1 and math-2 as
candidates followed by an error that math-2 is not a valid version.

Signed-off-by: Andrei Horodniceanu <a.horodniceanu@proton.me>

Change PackageSupplier interface to accept VersionRange ...

This is a leftover of the time when everything in dub accepted Dependency.
While the mess had been untangled, doing so on this interface proved harder,
as there is no good way to deprecate it in a fully backward-compatible manner
without introducing a lot of overhead (a new type). Instead, this uses
a middle ground approach, where the external implementers (which most likely
do not exists) would break (although the fix is trivial), but callers would not.

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

Avoid needless string concat in log calls

fix: parse version from filesystem supplier correctly

Replace calls to NativePath.toString() with .name ...

This has been deprecated in vibe-core and only triggers with 'library-nonet'.

Filesystem package supplier updated

Split-up package suppliers into individual modules