pw_thread: Mark legacy function* / void* constructor as deprecated

pw::thread::Thread now takes a pw::Function<void()>, which should be
used in place of the void(void*) function pointer and void* argument.

For example, replace code like the following:

  void CallBar(void* foo) {
    static_cast<Foo*>->Bar();
  }

  void StartThread() {
    Foo foo;
    thread = Thread(options, CallBar, &foo);
    ...
  }

with a lambda:

  void StartThread() {
    Foo foo;
    thread = Thread(options, [&foo] { foo.Bar(); });
    ...
  }

Bug: b/367786892
Change-Id: I6639ee94a201600cd0f0644fe4ab2c79a1492080
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/236454
Docs-Not-Needed: Wyatt Hepler <hepler@google.com>
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
Reviewed-by: Ewout van Bekkum <ewout@google.com>
Commit-Queue: Wyatt Hepler <hepler@google.com>
Pigweed-Auto-Submit: Wyatt Hepler <hepler@google.com>