Debian trixie support

Description

With the new Debian stable release, installation and build scripts for trixie should be implemented.

Tasks

• Add support for Debian trixie.
• Subscribe to relevant upstream tickets:
  • Support for Debian Trixie · Issue #1070 · openresty/openresty
  • Debian repository lacks Release file compatible with Debian ≥ 13 · Issue #1054 · openresty/openresty
• Switch CI to build Tor and OpenResty instead of using upstream packages.
• Documentation update.
• Merge !99 (merged) once OpenResty packages are available and CI passes.

Time estimation

• Complexity: very small (0.5 day)
• Uncertainty: low (x1.1)
• Reference (adapted)