tests: pkg/sql/opt/xform too sensitive to internal IDs

The git history of the tests in pkg/sql/opt/xform, specifically on testdata/external/*, show that every modification to the internal debugging tool some distance away in crdb_internal causes churn in these tests. Validating the content of crdb_internal is not the responsibility of these tests, so they should be adjusted to be less specific about unrelated changes in another part of the system, e.g. by regex'ing out the IDs before asserting their expected output.

Jira issue: CRDB-36791