Fix thread-local shutdown of RecordingStream on Mac and WIndows

[emilk]

• Original bug: Crash on shutdown when using thread local recording stream, Mac only (?) #2889
• Hacky fix: Fix crash when using RecordingStream::set_thread_local on macOS  #3929

Calling RecordingStream::set_thread_local on Mac and WIndows used to cause a crash during shutdown (#2889). In #3929 we replaced this with an ugly, arbitrary sleep instead.

This sleep has two downsides:

• It adds latency during shutdown to Mac
• It may not be enough to flush the pipe

A better fix would do something like:

while !flushed() {
    thread.yield()
}

The problem is we cannot use any channels for this, so we would need to rely on atomic bools and similar.

[Wumpf]

We're seeing the same issue on Windows as well.

[emilk]

Upstream issue:

• macOS: panic when using std::thread::current in thread_local Drop implementatiopn rust-lang/rust#116933