Adds two winget-sourced Windows FMAs:
- R (RProject.R) -> 'R for Windows', Inno Setup exe, machine scope
- Git (Git.Git) -> 'Git', Inno Setup exe, machine scope
Both use custom Inno install/uninstall scripts (no MSI ProductCode) with
registry-UninstallString-based uninstall and fuzzy name matching, since
their ARP DisplayName embeds the version ('R for Windows <ver>', 'Git
version <ver>').
test-fma-windows-pr-only.yml: add has_r/has_git detection and removal of
the runner's pre-installed R and Git. Git for Windows provides the Git
Bash 'bash' the workflow uses, so the apps.json filtering is split into
its own step that runs before Git removal, and validation runs 'go run
-buildvcs=false' (so Go does not invoke the now-removed git for VCS
stamping).
SSMS was investigated but intentionally skipped: SSMS 21/22 is a Visual
Studio online bootstrapper (no MSI ProductCode, multi-GB network
install), which is a fragile FMA candidate, and the runner has no
standalone SSMS to uninstall.
<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit
* **New Features**
* Added support for Git (Windows) with automated install/uninstall and
UI icon.
* Added support for R for Windows with automated install/uninstall and
UI icon.
* Windows testing workflow now detects and conditionally prepares
environments when Git or R are present.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
Allen Houchins
77b2cdcc6c