Remove php parser

[barryvdh]

Summary

Remove the PHP Parser. It was only used in edge-cases. The ContextFactory can be used to get the class aliases, similar to it being used in the rest of the code.
Only the realtime facades are using the php-parser besides that, and those are always the same format in the stubs, so just as well just regex them.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• Misc. change (internal, infrastructure, maintenance, etc.)

Checklist

• Existing tests have been adapted and/or new tests have been added
• Update the README.md
• Code style has been fixed via composer fix-style