ci: Add JDK25 to CI matrix, pin Actions to specific commits

[tguzik]

This PR:

• Adds JDK25 to the CI matrix to ensure tests still pass on this version
• Adds additional dependency pre-release version number patterns to the ignorelist
• Pins GitHub Actions to specific commits
• Pins DevEnv and nixpkgs versions to latest stable versions:
  • Sticking with DevEnv 1.11.1 until latest bugfix releases from the 2.x line are available in the main channels - ran into a couple of issues with scrollback and GPG input capture in the interactive mode.