[llvm] [llvm]Add a simple Telemetry framework (PR #102323)

[James Henderson via llvm-commits]

https://github.com/jh7370 commented:

The llvm_telemetry_design.png file needs updating with the new type names.

I've gone through everything except the tests again. Mostly, the code looks good, with the Serializer interface being the main exception. I'll look at the tests tomorrow.

https://github.com/llvm/llvm-project/pull/102323