pants: target sources glob expansion failure warning needs followup work

In #5769, we added a warning, or an error, if any of the elements in a globs(), rglobs(), zglobs(), or a literal file list provided as a sources= or bundles= keyword argument in a target definition. We pull in the logging crate to perform the warning, but the macro provided (warn!()) doesn’t seem to print anything anywhere I can find (although eprintln!() works!).

As a result of that PR, using --glob-expansion-failure=warn should use warn!() to describe to the user what target and what argument was being hydrated when a glob was expanded to nothing. This is done with --glob-expansion-failure=error by simply raising, producing the great native engine stack trace, e.g.:

Exception message: Build graph construction failed: ExecutionError Received unexpected Throw state(s):
Computing Select(Specs(dependencies=(SingleAddress(directory=u\'testprojects/src/python/sources\', name=u\'some-missing-some-not\'),)), =TransitiveHydratedTargets)
  Computing Task(transitive_hydrated_targets, Specs(dependencies=(SingleAddress(directory=u\'testprojects/src/python/sources\', name=u\'some-missing-some-not\'),)), =TransitiveHydratedTargets)
    Computing Task(transitive_hydrated_target, testprojects/src/python/sources:some-missing-some-not, =TransitiveHydratedTarget)
      Computing Task(hydrate_target, testprojects/src/python/sources:some-missing-some-not, =HydratedTarget)
        Computing Task(hydrate_sources, SourcesField(address=BuildFileAddress(testprojects/src/python/sources/BUILD, some-missing-some-not), arg=sources, filespecs={u\'exclude\': [], u\'globs\': [u\'*.txt\', u\'*.rs\']}), =HydratedField)
          Computing Snapshot(Key(val="PathGlobs(include=(u\\\'testprojects/src/python/sources/*.txt\\\', u\\\'testprojects/src/python/sources/*.rs\\\'), exclude=(), glob_match_error_behavior=\\\'error\\\')"))
            Throw(PathGlobs expansion failed: Throw(Globs did not match. Excludes were: []. Unmatched globs were: ["testprojects/src/python/sources/*.rs"]., "<pants native internals>"))
              Traceback (no traceback):
                <pants native internals>
              Exception: PathGlobs expansion failed: Throw(Globs did not match. Excludes were: []. Unmatched globs were: ["testprojects/src/python/sources/*.rs"]., "<pants native internals>")

However, the warning message we currently display would only contain the end of that: Globs did not match. Excludes were: []. Unmatched globs were: ["testprojects/src/python/sources/*.rs"].. This needs to be fixed for --glob-expansion-failure=warn to be usable.

There are multiple unit tests to unskip in tests/python/pants_test/engine/legacy/test_graph_integration.py once these are resolved. This was left as a FIXME in that PR.