[MRELEASE-799] Preserve explicit previous-version property references

[goutamadwant]

Fixes #1004 (MRELEASE-799).

release:update-versions fails when a plugin dependency references a reactor artifact's previous release through a property, while the equivalent literal version is preserved. For example, a project at 2.0-SNAPSHOT using its own 1.0 release through ${previous.version} cannot advance to 2.1-SNAPSHOT.

Preserve locally defined literal property values that refer to a different original artifact version. Cache original values as version references are visited, including CI-friendly properties before project-version rewriting. After rewriting, reject shared properties that would change a preserved reference. This retains conflict detection regardless of reference order and applies through the shared POM rewrite phases.

Validation:

• Reproduced the failure with the unchanged master plugin; the patched release:update-versions advances the project and retains ${previous.version} at 1.0.
• Added native POM rewrite regressions across update-versions, release, development, and branch phases, including current-version updates, literal references, shared-property conflicts in both orders, and CI-friendly version conflicts.
• mvn -Prun-its verify passed with Maven 3.9.16 and Java 21.
• Final focused regressions passed on Java 8 and Java 21.

This change is limited to locally resolvable literal property values; it does not add resolution of inherited properties or composed expressions.

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.