Follow-up from "Add API for creating limit exclusions"

The following discussion from !116518 (merged) should be addressed:

• @mhamda started a discussion: (+1 comment)

  thought (non-blocking/out of scope):

  Is the current factory name (storage_limit_excluded_namespace) confusing? It reads as if it creates a namespace rather than a storage limit exclusion.

  Should we rename it to something more appropriate like namespace_storage_limit_exclusion or storage_limit_exclusion_for_namespace?