Feature: Implement fll_program_standard_signal_received_wait().

Feature: Implement fll_program_standard_signal_received_wait().

The `fll_program_standard_signal_received_wait()` is now added because a lot of this code is repeated forr every single FLL program.

The `fll_program_standard_signal_received()` is refactored to return a status code to match the newly added `ll_program_standard_signal_received_wait()`.

The `status_signal` can now be moved into the main program settings structure.
The `status_signal` is renamed to `signal_status` to keep the naming more consistent.

This also exposes and fixes a race condition in how the pre-existing threaded signal handling is being used.
The check for `program.signal.id` that then opens a signal via `f_signal_open()` in the thread is not necessary because the signal id from the parent thread is preserved.
The `f_signal_close()` in the thread ends up prematurely closing the signal because the parent thread signal id is passed to the child thread.
The `main->program.signal.id == -1` checks in the signal check functions end up preventing the interrupt cancel from being triggered because of the `f_signal_close()` being called in a separate thread that shares the same signal id.