Don't ignore errors raised by `PyErr_WarnFormat` in `warn_about_fork_with_threads`
Instead, ignore the warnings in all test code that forks. (That's a lot of functions.)
In `test_support`, make `ignore_warnings` a context manager (as well as decorator),
and add a `message` argument to it.
Also add a `ignore_fork_in_thread_deprecation_warnings` helper for the deadlock-in-fork
warning.
- re-enable test_fcntl_64_bit on Linux aarch64, but disable it on all
Android ABIs
- use support.setswitchinterval in all relevant tests
- skip test_fma_zero_result on Android x86_64
- accept EACCES when calling os.get_terminal_size on Android
Fix test_timeout() of test_concurrent_futures.test_wait. Remove the
future which may or may not complete depending if it takes longer
than the timeout ot not. Keep the second future which does not
complete before wait(). Make also the test faster: 0.5 second instead
of 6 seconds, so remove @support.requires_resource('walltime')
decorator.
