Fix microsoft-git release version parsing

[scaryrawr]

Summary

• support current microsoft/git release tag shapes, including multi-digit VFS revisions and explicit RC versions
• keep latest/current/lts resolving to the latest stable release
• preserve older amd64 legacy Debian package compatibility while avoiding incompatible legacy packages on other architectures
• add targeted microsoft-git scenarios for latest, legacy package, multi-digit VFS, and explicit prerelease installs

Validation

• bash -n src/microsoft-git/install.sh test/microsoft-git/*.sh
• jq empty src/microsoft-git/devcontainer-feature.json test/microsoft-git/scenarios.json
• devcontainer features test -f microsoft-git --skip-autogenerated .