Preserve action ref when changing action

[Wanbinyu]

What changed

• Make ChangeAction.newVersion optional.
• Preserve each matching action existing tag, branch, SHA, or absent ref when newVersion is omitted.
• Keep explicit version replacement behavior unchanged.
• Regenerate META-INF/rewrite/recipes.csv.

Testing

• ./gradlew test --tests org.openrewrite.github.ChangeActionTest --rerun-tasks --stacktrace
• ./gradlew recipeCsvGenerate recipeCsvValidate --stacktrace
• ./gradlew clean build --stacktrace --no-daemon
• git diff --check

The tests cover tag, branch, and SHA refs; declarative YAML activation without newVersion; composite action definitions; and preservation of inline comments and with: configuration.

• Fixes Replace action but leave configuration as is #80