Consolidate Release Workflows

[ObliviousHarmony]

These workflows are more of a black box:

Workflows

• build-release-zip-file.yml: Creates a ZIP archive for WooCommerce Core. This is used in the release process.
• cherry-pick.yml: Used in the release process to automatically create a release branch cherry-pick PR when a PR is assigned a milestone for a version with a release branch.
• mirrors.yml: Mirrors the built WooCommerce plugin to a separate repository.
• package-release.yml: Builds and releases the selected package.
• post-release.yml: Creates a pull request after a release is made that updates the changelog and version in trunk.
• prepare-package-release.yml: Prepares a package for release by updating the versions and changelogs.
• release-code-freeze.yml: On the day of the code freeze this workflow creates a release branch and sets up trunk for the next release.
• release-wc-beta-tester.yml: Creates a release for the beta tester plugin.
• nightly-builds.yml: Builds WooCommerce Core nightly and replaces the "nightly" release.
• pull-request-post-merge-processing.yml: Runs after a pull request is merged to trunk. This adds applicable milestones and labels.
• pr-build-live-branches.yml: Builds the WooCommerce plugin and sends it to an internal testing site.

These workflows are all pretty tightly coupled to the release process. We can probably identify things as build-related and release-related. Some of them are specific to WooCommerce Core, but if we create a separate mirror repository, they would probably live there? It's probably best to not touch the Core release process ones and instead focus on centralizing things like releasing the beta tester and packages. Reach out to stakeholders on how maybe we can consolidate the others.

@jonathansadowski do you have any thoughts?

[ObliviousHarmony]

If we want to move towards releasing from a separate plugin repo we can chat about what that might look like too and I can make that happen 😄