PHP Composer: Publish Package MVP

What does this MR do?

Adds an MVP publishing for PHP Composer packaged.

Given a branch/tag name, it creates a package object with the proper package name (from composer.json) and version (from branch/tag name).

There's no file upload as it's not required for composer (the package will come from the archive API).

It also adds the sha of the branch/tag as metadata for the package as it will be needed for retrieving the composer.json file in future MR's when retrieving the package contents.

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Part of #214727 (closed)