Testing: kernel32:debugger, there's sometimes the following error:
debugger.c:1760: Test failed: unexpected instruction pointer 778B2A0C

Current test code has a workaround when this happens on last thread, but
this is clearly not sufficient.

Fix the test so that it grabs the thread context only in a place we're
sure it's in stopped state at breakpoint instruction.
(Current code likely catches cases where the thread is in bp signal
handling).

Rewrote the test to be in more logical order.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=53143