Stop mixing CPU and wall-clock time in the GHC profiler
Summary
When exploring the behavior of the GHC profiler in #21764 (closed), it surfaced that wall-clock time is estimated when doing unsafe foreign calls, but CPU time is estimated otherwise.
This state of affairs makes difficult to interpret the results of profiling. In order to learn if one is seeing wall-clock time, CPU time, or an unspecified mix of both, one needs to understand the call graph, which is potentially large and complicated.
If people really wants to use the GHC profiler to measure wall-clock time, probably the best option is to put it behind a flag.
- GHC version used: 9.2