[lldb] Fix crash in BreakpointSite::BumpHitCounts (#166876)
Fix crash in `BreakpointSite::BumpHitCounts` due to missing
synchronization. When bumping the hit count, we were correctly acquiring
the constituents mutex, but didn't protect the breakpoint location
collection. This PR fixes the issue by making the iterator returned by
the collection a `LockingAdaptedIterable`.
rdar://163760832