[mono][jit] Emit profiler enter after jit attach; leave before detach (#44345)

[mono][jit] Emit profiler enter after jit attach; leave before detach (#44345)

* [jit] Emit profiler enter after jit attach; leave before detach

profiler enter code (such as mono_trace_enter_method) must not be
called before a thread attaches to the runtime - otherwise calls like
`mono_domain_get()` will return NULL unexpectedly and then crash.
When detaching, we should call the profiler leave code before the
detach, and suppress it on return.

Simple repro (that relies on pal_signal.c SignalHandlerLoop - which is
a background thread from System.Native that calls back into managed
when there's a SIGCHLD): compile and run this program with `MONO_ENV_OPTIONS=--trace`

```csharp
using System;
using System.Diagnostics;

namespace Repro
{
    internal class Program
    {
        private static void Main(string[] args)
        {
            using (Process myProcess = new Process())
            {
                    myProcess.StartInfo.UseShellExecute = true;
                    myProcess.StartInfo.FileName = "echo";
                    myProcess.StartInfo.Arguments = "hello from shell";
                    myProcess.StartInfo.CreateNoWindow = true;
                    myProcess.Start();
                    myProcess.WaitForExit();
            }
            Console.ReadKey ();
        }
    }
}
```