[llvm] [llvm-profdata] Emit warning when counter value is greater than 2^56. (PR #69513)

[via llvm-commits]

zmodem wrote:

Agreed that it maybe time to rethink the error handling.

We'd definitely want an option to treat these pathological counts as an error.

Maybe just having a `-Werror` flag is enough for that, or we might need more granular flags. I don't know enough about what other non-fatal errors there are, and their seriousness.

https://github.com/llvm/llvm-project/pull/69513