feat: add git-root-search support to JReleaser action

[raphaeldelio]

Summary

Adds git-root-search input parameter to the JReleaser action to support monorepo configurations.

Why This Was Necessary

In monorepo setups where the working directory is a subdirectory (e.g., clients/java), JReleaser fails with "Not a git repository" because it can't find the .git directory at the repository root. The JRELEASER_GIT_ROOT_SEARCH environment variable enables JReleaser to search up the directory tree to find the .git folder.

Changes

• Added git-root-search input parameter to .github/actions/jreleaser/action.yml (default: 'true')
• Added JRELEASER_GIT_ROOT_SEARCH environment variable to JReleaser execution
• Automatically applies to all JReleaser invocations in release.yml and early-access.yml

No Breaking Changes

• Fully backward compatible - defaults to 'true' which is safe for all repository types
• Optional parameter - existing consumers require no changes
• Can be disabled by setting git-root-search: 'false' if needed