feat: Support SSH session recording configuration

[Qup42]

• [x] read the CONTRIBUTING guidelines
• [x] raised a GitHub issue or discussed it on the projects chat beforehand
• [x] added unit tests
• [ ] added integration tests
• [ ] updated documentation if needed
• [ ] updated CHANGELOG.md

This PR makes the necessary backend changes to support SSH session recording. This consists of handling the recorder and enforceRecorder fields^1 of the ssh ACL rules. Providing a compatible recorder is not part of this PR.

Resolves #1793

[Qup42]

Qup42/loghead is a simple recorder that can be used with custom control planes. tailscale/tsrecorder only works with the standard control plane.