Define a proper deprecation policy for frameworks

[sentrivana]

Right now, we almost never drop framework support explicitly. We should be more mindful of how and when we drop support for frameworks.

• determine and define minimum versions for all currently integrated frameworks
  • the toxgen script can help with this since it automatically determines the lowest supported version using package metadata
• enforce these (from the next major)
• when working on a new major, go through frameworks and see what the new effective minimum version is and update it
  • ...and call this out in the release notes
  • see Drop support for old versions of frameworks in POTel #4049 for POTel
• be explicit about how this works in our documentation