[llvm] [CAS] Add OnDiskGraphDB and OnDiskKeyValueDB (PR #114102)

[Thurston Dang via llvm-commits]

thurstond wrote:

> Attempt 2 here: #164493
> 
> I didn't figure out the real reason of failure last time. It was due to not all the fields in `std::array` is initialized.

Thanks for the quick fix!


https://github.com/llvm/llvm-project/pull/114102