Support toggling static/dynamic plugin builds

[dominiklohmann]

📔 Description

This PR enables static plugin builds.

📝 Checklist

• All user-facing changes have changelog entries.
• The changes are reflected on docs.tenzir.com/vast, if necessary.
• The PR description contains instructions for the reviewer, if necessary.

🎯 Review Instructions

Commit-by-commit. I suggest we peer-review this in a call because there are some things in here whose need may not be entirely obvious.

This can already be reviewed before it's out of draft mode—the first commit contains the enabling CMake and plugin framework changes. Later commits simplify the plugin CMake. Ready for review.

[dominiklohmann]

Peer-reviewed with @tobim.

[tobim]

Tested locally. Verified that type id clashes of static plugins result in a readable linker error.

[dominiklohmann]

I only rebased to fix the merge conflict in the CHANGELOG entry after approval.