Publish openassetio-mediacreation to PyPI

[foundrytom]

What

Publish this to PyPI as openassetio-mediacreation for 3.7+ once #10 and #9 and #12 are done. And OpenAssetIO/OpenAssetIO#717.

• No sdist as it shouldn't be required, and could result in non-deterministic installs of any given tag due to changes in TraitGen (unless this is pinned to a patch version).

Why

This will greatly simplify the development of prototype integrations.

Notes

• Switch MC to using openassetio-traitgen #10 removes the generated Py code from the repo, the PyPI published package should include pre-build Python files (ie: not run traitgen locally on the target machine), this ensures the existing releases are always usable.

• This should be 1.0.0a2 as a1 was released via tag only.

• Do this before Migrate managementPolicy traits to MediaCreation repo OpenAssetIO#717