Implement identifier reassignment in XSLT profile resolution implementation

[wendellpiez]

User Story

With PR #1424 we have new constructions in the profile model supporting new functionality. This functionality needs to be implemented in the XSLT-based profile resolver.

Goals

The following work needs to be completed.

• Develop XSLT support for identifier reassignment
• Develop unit tests that test all reassignment features

Dependencies

Merge any prior PRs updating tests to ensure unit tests are up-to-date.

Updated specification (#1474)

The diff on the profile metaschema with PR for #1424 will show the new features.

Acceptance Criteria

• Test are verified to cover all reassignment features
• XSLT implementation passes the tests
• All OSCAL website and readme documentation affected by the changes in this issue have been updated. Changes to the OSCAL website can be made in the docs/content directory of your branch.
• A Pull Request (PR) is submitted that fully addresses the goals of this User Story. This issue is referenced in the PR.
• The CI-CD build process runs without any reported errors on the PR. This can be confirmed by reviewing that all checks have passed in the PR.

[wendellpiez]

For interest, the new construct permits mapping identifiers from catalog sources to enable more flexible control mixing/matching via ID reassignment.

This being said, the syntax is a bit hard to read from metaschema source, so let's start with unit tests (validated to an appropriate schema).