Add macro for uninstall target and fix symlink tracking

[jmsexton03]

Summary

• Add add_uninstall_target macro to create reusable uninstall target
• Track libamrex symlink in install manifest for proper cleanup
• Add AMReX_cmake_uninstall.in template for uninstall script

Additional background

Previously, the libamrex symlink was not tracked in the install manifest. Newer CMake versions provide better ways to reference source locations using variables instead of hardcoded paths, allowing manifest information to be stored more accurately. The new macro also prevents conflicts when multiple projects using AMReX each try to create their own uninstall targets.

Checklist

The proposed changes:

• fix a bug or incorrect behavior in AMReX
• add new capabilities to AMReX
• changes answers in the test suite to more than roundoff level
• are likely to significantly affect the results of downstream AMReX users
• include documentation in the code and/or rst files, if appropriate