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`;

Remove 'unknown' version ...

It was never used.

Integrate `dependencyBuildSettings` into dependencies ...

Because those are specified in `dependencies`,
they should be stored alongside them.
Unfortunately this will slihtly increase memory usage in the common case,
but unlikely to a point where it would be problematic.

This is technically a breaking change as a field is getting removed,
however this struct has been manipulated a few times in breaking ways,
and it's unlikely `dependencyBuildSettings` is being used outside of dub,
given how recent it is and how narrow its usage is.
However, as `dependencies` is likely to be widely used, a compatibility
type and an `alias this` are provided not to break client code.

reduce FS access count for main file generation ...

as all the sourcePaths are checked and the last one is used, we just go
through all the sourcePaths in reverse and break when the first one is
found.

only do main file searching when neccessary

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

Add support for coverage at compile-time (CTFE)

Implement injection of source files from dependencies into parent final binaries (executed/shared libraries)

fix CLI --print-builds implementation

fix Issue 1645: the DFLAGS env variable is not handled when --build is passed

Add environment variables to BuildSettings (#2121)

Refactor import. inet.path is publicly imported from inet.url, but only symbols from inet.path are used.

Mutually exclude mainSourceFile of different configurations ...

Unless explicitly added to sourceFiles, a configuration will exclude
other configurations' mainSourceFile's.

Move git version detection into a separate module.

Revert "Add flag --submodules to add git submodules in the project folder as available packages."

make git submodule version checks use -C with relative --git-dir instead of absolute --git-dir. ...

With absolute --git-dir, we are unable to find the .gitmodules.

Add flag --submodules to add git submodules in the project folder as available packages. ...

Adjust git version determination to support submodule folders

Change toolchainRequirements fields to Dependency. ...

Also removes some API clutter from Compiler and PackageRecipe.

Fix compile error on DMD 2.083.1.

toolchainRequirements recipe support

infer unspecified version filters ...

- otherwise of little use as all dependencies need to have specified
  version filters before this can be used
- also version identifiers are fairly easy to grep for
- cache inferred version filters
- still allows explicit specification for packages that use version
  identifiers in mixins

Revert "implement "minDubVersion" field"

better error message

save function call

implement minDubVersion check ...

fix #1531

Add build type syntax

Rename Path to NativePath. ...

Matches the changes done in vibe.d 0.8.x and vibe-core.

Avoid GC allocations in DependencyVersionResolver.getChildren.

Perform package linting only for packages in the current project.