Replace control list locks with RWLocks

Replace control list locks with RWLocks

towards fixing #6238 and #6096.

GUI thread:
#2  Glib::Threads::Mutex::Lock::Lock
#3  Evoral::ControlList::eval
#4  Evoral::Control::get_double
#5  ARDOUR::AutomationControl::get_value
#6  ProcessorEntry::Control::control_changed
..
#15 PBD::Timer::timeout_handler

at the same time: Audio Thread (try-lock, fails)

#0  Evoral::Curve::rt_safe_get_vector
#1  ARDOUR::Amp::setup_gain_automation
#2  ARDOUR::Route::process_output_buffers

Due to the failed try-lock.. AMP::_apply_gain_automation
is false. and Amp::run() uses a different gain factor.
-> click.