docs: add Driver-Server Version Compatibility Matrix

[pmishchenko-ua]

No description provided.

[cursor]

PR Summary

Low Risk
Documentation-only change to the release guide with no runtime or packaging impact.

Overview
Adds a Driver-Server Version Compatibility Matrix section to RELEASE.md after the failed-releases notes.

The section documents how maintainers should update the matrix on each release (new row per driver version, sourcing engine support from CI history for older tags and from the SingleStore EOL policy plus RCs for releases from v8.0.3 onward). It includes a table mapping driver versions 6.0.2 through 9.0.0 to release dates and supported engine versions.

^{Reviewed by Cursor Bugbot for commit bec5327. Configure here.}