[9.1.0] Refactor flag aliases to be passed around as labels

[bazel-io]

Forked from #28506

[bazel-io]

Cherry-pick was attempted but there were merge conflicts in the following file(s). Please resolve manually.

src/main/java/com/google/devtools/build/lib/analysis/starlark/FunctionTransitionUtil.java
src/main/java/com/google/devtools/build/lib/analysis/starlark/StarlarkTransition.java
src/main/java/com/google/devtools/build/lib/rules/config/ConfigRuleClasses.java

cc: @bazelbuild/triage

[gregestren]

I think this supports rules_python flag aliases: bazel-contrib/rules_python#3450 (comment)

[iancha1992]

Cherry-picked in #28851