Add public APIs to set trace and profile function in other threads.

[pablogsal]

Currently, we have two public c-apis to set tracing and profile functions: PyEval_SetProfile and PyEval_SetThreadTrace. This allows to set tracing and profiling functions in the calling thread. This works well, but is, unfortunately, is limited because there is no way for debuggers and profilers to set the tracing and profiling functions in all existing running threads, only the ones that are newly created. This makes it impossible to reliable profile or debug already running applications using public APIs or to allow to activate/deactivate said profilers or debuggers.

There are two exposed APIs that are private (have a leading underscore) that do what we need: _PyEval_SetProfile and _PyEval_SetTrace. Unfortunately, these APIs are not fully public and they don't generate audit events.

I propose to expose public-facing versions of these APIs so profilers and debuggers can set their tracing/profiling functions in all existing threads.