[llvm] [LLVM][DWARF] Create thread safe context for DWP DWARFContext (PR #68262)

[Greg Clayton via llvm-commits]

clayborg wrote:

So sounds like we need to change this patch to propagate the "ThreadSafe" from one context to any child DWARFContext things (like for owned .dwp and .dwo contexts. I would recommend adding a new virtual function to DWARFContext:
```
virtual bool IsThreadSafe() = 0;
```
Then have ThreadUnsafeDWARFContextState override this and return false, and ThreadSafeState override it return true. Then it will be easy to propagate the setting using the current "DWARFContext::State" iivar from a DWARFContext to create another.


https://github.com/llvm/llvm-project/pull/68262