[Coroutines] Conditional elide coroutines based on hot/cold information (#162276)HEADmain

Unconditionally eliding all `[[clang::coro_await_elidable]]` coroutines
is not good.

For example,

```
Task bar();
Task foo(bool b) {
     if (b) [[unlikely]] {
         co_await bar();
     }
}
```

Assume Task is marked with `[[clang::coro_await_elidable]]`, now we will
always elide the call to `bar()` into the frame of `foo()`. But this may
be a regression instead of an optimization if `b` is always false.

This patch tries to mitigate the problem by leveraging hot/cold
information. This can be optimized further in the future but at least
this patch makes things better.

This patch was originally written by ChuanqiXu9 (#145831), but stalled
during PR review because the diagnostics were not integrated with
the existing optimization remarks. I rebased the original patch,
integrated it with the optimization remarks, and did a couple of smaller
cosmetic changes (e.g., made the test case expectations more
targeted, etc.)

Co-Authored-by: Chuanqi Xu <yedeng.yd@linux.alibaba.com>

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