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

[James Henderson via llvm-commits]

https://github.com/jh7370 commented:

I've been thinking about it a bit more, and I think that it would make sense to have a single upstream implementation that writes a representation of some kind (JSON is fine) to a file. This would be off by default, but could be enabled via an option somehow (perhaps keep it in LLVM-only code and add a runtime option). This would have two benefits: 1) it would serve as a concrete example for vendors how to extend the interface, and 2) it could be used for testing the basic telemetry information is working in an end-to-end manner, via lit tests, in a way that the current unit tests can't really show. Thoughts?

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