Ensure that we only have one writer to the module trace file at a time by using LLVM's `LockFileManager` utilities, similarly to `ModuleInterfaceBuilder`
Resolves rdar://76743462
Follow programming guidelines for these getters more closely and have them return a non-owning view of the underlying data instead of relying on callers to take const references to the copy that is returned here.
T *const does not prevent logically non-const accesses to the underlying data, it merely indicates that the pointer value itself is const. This modifier can be cast off by a copy, so it's not generally what you want here. Switch to const T * instead.
