[BUGFIX]: composer updates to fix Strauss issues causing tests to fail.

[defunctl]

I think I'll still submit a PR after this to convert this to slic since that's what the rest of the company uses, but this:

1. Fixes broken test framework caused by Strauss prefixing dependencies codeception uses. The fix is to not delete prefixed vendor packages, but this makes development more prone to error because your IDE will show both prefixed and normal package namespaces and if a developer uses a normal namespace, that will cause conflicts when this is installed with other WordPress plugins. This may get fixed in Strauss 1.0..
2. Replaces all composer installation with the ramsey/composer-install action, which automatically handles caching out of the box.
3. Re-enables composer validate step and fixes this by adding composer/installers package.
4. Fixes docker permissions by passing the current user that is running the GitHub action to docker.