Packagist deprecated the original `packagist.org/p/username/package` endpoint in favor of v2 `packagist.org/p2/username/package` endpoint. Because of this, new packages aren't being found using v1.

This PR updates the Packagist service to use the new endpoint.

Some packages don't return the same data structure as others with the new api endpoints. This changes the validation schema to account for the potential differences.

Address issues raised by @chris48s in badges#6508, which this PR is base on.
Includes:

* Remove getDefaultBranch() from base class for it is no longer used.
* Change try-catch statement syntax to align code style.
* Rename findRelease() to findLatestRelease() for clarity.

…lease

* Change BasePackagistService.decompressResponse to static
  method BasePackagistService.expandPackageVersions.
* Fix expandPackageVersions implementation.
* Add unit test for the function.

* extend BasePackagistService.findLatestRelease to also handle
  PackagistVersion.
* remove PackagistVersion.transform.

* Update findLatestRelease to throw NotFound itself.
* Update PackagistLicense and PackagistVersion and remove the
  NotFound throwing logics.

* The test was on a false assumption that '__unset' might appear
  inside an array leaf while the composer's MetadataMinifier::minify
  never does thing recursively. The '__unset' should be value of the
  top level key.

* improve jsDoc to the PackagistPhpVersion class.
* simplified PackagistPhpVersion.getPhpVersion logics and remove
  fetchDev from getPhpVersion method.
* update tests accordingly.

* migrate expandPackageVersions usage to handle to simplify getPhpVersion
  logics.

* fix potential issues where the versions array is unexpanded.

* rename method "transform" into "getVersion" to better describe its
  use.
* moved usage of expandPackageVersions into handle function.

* Rename BasePackageService.fetch method as fetchRelease.

* Add a new fetch method that calls fetchRelease. Extract
  all expandPackageVersions calls from handle methods
  of different child class into fetchRelease.

* More reasonable defination.

* Move method findSpecifiedVersion from PackagistPhpVersionService
  to BasePackagistService as a static method.

* moved method specific test data into the test itself.

* rename allVersionSchema into composerMetadatApiSchema to better
  describe what it is.
* make composerMetadatApiSchema the default value of schema in
  fetchVersions, fetchRelease and fetchDev. Remove explicit import
  and use of composerMetadatApiSchema from child services.

* unify all version search into a single
  BasePackagistService.findVersion method.

* Add test coverage of findSpecifiedVersion.
* Add test coverage of findLatestVersion.

* Add a includeDefaultBranch flag in findVersion to also search
  for metadata of default branch.

* simplified parameter list of getPhpVersion

* resurrected some of the relevant older tests.
* remove the api json array expand logics from test.

* Moved expandPackageVersions calls into fetchRelease and fetchDev.
  The return values needed to be expanded anyway.
* Rename fetchVersions as fetch to make it closer resembling the
  current stable version.
* Improve documentations.

* Use fetchRelease instead of fetch. Less API calls.

* Only fetch the ~dev.json endpoint if needed.

* export error message string as constant and reuse in tests

* Move all messages constant to base class file. Ensure *.service.js
  exports only services or collection of services.

* Off load the default branch searching logics from findLatestRelease
  to findDefaultBranchVersion. Implement Packagist default logic to
  search for default metadata to display.

* fix documentation in fetchRelease and fetchDev.
* use await keyword in usage of fetchRelease and fetchDev to get
  reasonable results.