[clang] [clang][coverage] Add opt-in call continuation counters for coverage (PR #201079)

[Alan Phipps via cfe-commits]

evodius96 wrote:

> @evodius96, @efriedma-quic @justincady if you have some bandwidth, could you please help review this ?

Thank you for doing this! It will be a few days before I can dive in. My goal is to look at it next week.

https://github.com/llvm/llvm-project/pull/201079