Removing `measureme` tracing crate

[Stypox]

The measureme tracing crate is currently used to trace rustc, however the tooling around it is a bit limited, since it's mostly intended for compiler profiling (where tasks might be less repetitive). The interface of measureme functions and the data format are quite basic and low level, and furthermore measureme requires passing a profiler object around. That's why we have switched to using the tracing library recently, which (when connected with a tracing_chrome layer), allows exporiting traces with lots of information which can be opened in visualization tools like https://ui.perfetto.dev. Since it might be confusing to have two different tracing infrastructures within Miri, I would suggest removing measureme, also considering that there have not been significant increments in code covered by measureme tracing calls in the last few years. I'm also pinging @Aaron1011 who introduced measureme in #1791: what do you think about removing it and use only tracing from now on?

[RalfJung]

I'm fine with removing the measureme machinery, but let's wait to see if someone needs it.

[RalfJung]

@saethlin recently used the measureme support in #4616. Not sure if that could have been just as easily profiled with the new infrastructure.