Mappings for repos defined in WORKSPACE are extremely annoying to verify given the chunked loading (we'd have to record which chunk the repo mapping was used in, and then load that chunk while verifying). This is extremely not worth the effort (especially since nobody really uses repo mappings in WORKSPACE) so we just don't record it.

This also means, during verification, we can safely use the main repo mapping without WORKSPACE (since repos defined in Bzlmod can't see stuff from WORKSPACE anyway).

Fixes #21289.