add support for vcpkg-configuration.json's baseline

[lukka]

Changes:

• the vcpkgGitCommitId input is optional, and the Git commit id can be fetched from :
  • vcpkg-configuration.json:
    - the file is searched with provided glob expression in vcpkgConfigurationJsonGlob input.
    - the baseline is searched using JSONPath $["default-registry"]["baseline"]
  • vcpkg.json:
    - the file is searched as usual/already (glob + ignore input).
    - the baseline is searched using JSONPaths (first hit wins):
    - $["builtin-baseline"]
    - $['vcpkg-configuration']['default-registry']['baseline']

Note: only the default-registry's builtin kind is supported, the kind git or filesystem are not supported.

[BurningEnlightenment]

I'm unsure where you discovered vcpkg.json > $['default-registry']['baseline'] its associated schema doesn't mention a default-registry key in the root object. Two additional test cases for the other two vcpkg.json based baseline searches would probably be useful.

Otherwise LGTM 👍