Use a version of the stack_sampling_profiler to create a thread to sample CallFunction. This is part of the work required to land LongTasks v2.

The profiler lives in base:
https://cs.chromium.org/chromium/src/base/profiler/stack_sampling_profiler.h?rcl=3148a21a852e1d31345793a43fbf77430a96e3e1&l=67

There is some work in making the profiler work for our use case. In fact, it currently does not sample the renderer process nor knows how to sample JS.

This work is also blocked on resolving concerns at TPAC concerning the LongTasks v2 API.