This test was removed long ago in eb0e3ba.

Signed-off-by: Damien George <damien@micropython.org>

The aim of this commit is to make it so that the existing thread tests can
be used to test the _thread module on the rp2 port.  The rp2 port only
allows up to one thread to be created at a time, and does not have the GIL
enabled.

The following changes have been made:
- run-tests.py skips mutation tests on rp2, because there's no GIL.
- run-tests.py skips other tests on rp2 that require more than one thread.
- The tests stop trying to start a new thread after there is an OSError,
  which indicates that the system cannot create more threads.
- Some of these tests also now run the test function on the main thread,
  not just the spawned threads.
- In some tests the output printing is adjusted so it's the same regardless
  of how many threads were spawned.
- Some time.sleep(1) are replaced with time.sleep(0) to make the tests run
  a little faster (finish sooner when the work is done).

For the most part the tests are unchanged for existing platforms like esp32
and unix.

Signed-off-by: Damien George <damien@micropython.org>

The existing thread_sleep1.py test only tests execution, not accuracy, of
time.sleep.  Also the existing test only tests sleep(0) on targets like rp2
that can only create a single thread.

The new test in this commit checks for timing accuracy on the main thread
and one other thread when they run at the same time.

Signed-off-by: Damien George <damien@micropython.org>