Preserve Git repository URLs for non-root release POMs

[goutamadwant]

Fixes #1457.

When a reactor POM is below the Git checkout root, release descriptor alignment removes path segments from the Git repository URL. For example, parent/pom.xml changes scm:git:https://example.com/team/project.git to scm:git:https://example.com/team, so pushing the release tag fails.

Preserve Git repository URLs in the shared descriptor alignment used by tag, branch, and rollback. Other SCM providers retain their existing directory alignment.

Validation:

• Reproduced the failed tag push on unchanged master using a disposable local Git repository; the patched plugin completes prepare, rollback, and branch, with remote refs checked.
• Added URL and phase regressions for root and nested POM layouts, Git URL forms, unchanged working directories, and SVN alignment.
• mvn -Prun-its verify passed with Maven 3.9.16 and Java 21.
• Focused regression tests passed on Java 8.

Checklist:

• This pull request addresses one issue.
• The description explains what changed, how, and why.
• The commit has a meaningful subject and body.
• Added regression tests that fail without the production fix.
• Basic verification passed through mvn -Prun-its verify.
• Integration tests passed with mvn -Prun-its verify.
• I hereby declare this contribution to be licenced under the Apache License Version 2.0, January 2004.
• In any other case, please file an Apache Individual Contributor License Agreement.