fix loading of repeated/concurrent modules (#55066)
More followup to fix issues with require. There was an accidental
variable reuse (build_id) that caused it to be unable to load cache
files in many cases. There was also missing check for a dependency
already being loaded, resulting in trying to load it twice. Finally, the
start_loading code may drop the require_lock, but the surrounding code
was not prepared for that. Now integrate the necessary checks into
start_loading, instead of needing to duplicate them before and
afterwards.
Fixes #53983
Fixes #54940
Closes #55064
