Add --enable_workspace flag (defaulting to true) to allow turning off WORKSPACE logic #20185
Description
Setting this flag to false should turn off all WORKSPACE related logic, including evaluating the WORKSPACE/WORKSPACE.bazel/WORKSPACE.bzlmod files at all, any WORKSPACE prefixes/suffixes, the LocalRepositoryLookupFunction (with some sort of replacement).
A blocker for this issue would be #18285; we currently still don't have a way to specify a local_repository/new_local_repository in a module extension.