Kernel: Don't attempt to yield execution in SleepThread(0) if there are no available threads to run.

With this we avoid an useless temporary deschedule of the current thread.

After hwtesting and reverse engineering the kernel, it was found that the CTROS scheduler performs no priority boosting for threads like this, although some other forms of scheduling priority-starved threads might take place.

For example, it was found that hardware interrupts might cause low-priority threads to run if the CPU is preempted in the middle of an SVC handler that deschedules the current (high priority) thread before scheduling it again.

Closes #1904

The regression was caused by a missing check in #2260.

The new behavior is consistent with the real kernel.

This fixes a potential bug where threads would not get removed from said list if they awoke after waiting with WaitSynchronizationN with wait_all = false

Kernel: Remove Thread::wait_objects_index and use wait_objects to hold all the objects that a thread is waiting on.

Kernel: Use different thread statuses when a thread calls WaitSynchronization1 and  WaitSynchronizationN with wait_all = true.

This commit removes the overly general THREADSTATUS_WAIT_SYNCH and replaces it with two more granular statuses:

THREADSTATUS_WAIT_SYNCH_ANY when a thread waits on objects via WaitSynchronization1 or WaitSynchronizationN with wait_all = false.

THREADSTATUS_WAIT_SYNCH_ALL when a thread waits on objects via WaitSynchronizationN with wait_all = true.

Kernel/Mutex: Propagate thread priority changes to other threads inheriting the priority via mutexes

The implementation is based on reverse engineering of the 3DS's kernel.

A mutex holder's priority will be temporarily boosted to the best priority among any threads that want to acquire any of its held mutexes.
When the holder releases the mutex, it's priority will be boosted to the best priority among the threads that want to acquire any of its remaining held mutexes.

This will be useful when implementing mutex priority inheritance.

Not all syscalls should cause reschedules, this commit attempts to remedy that, however, it still does not cover all cases.

Moved the HLE command buffer translation task to ServerSession instead of the HLE handler superclass.

Define a variable with the value of the sync timeout error code.

Use a boost::flat_map instead of an unordered_map to hold the equivalence of objects and wait indices in a WaitSynchN call.

Further implementation will happen in a future commit.

Fixes a regression.

The error code was taken from the 3DS kernel.

Split SessionRequestHandler::HandleSyncRequest into HandleSyncRequest, TranslateRequest and HandleSyncRequestImpl.

HandleSyncRequest now takes care of calling the command buffer translate function before actually invoking the command handler for HLE services.

KServerPorts now have an HLE handler "template", which is inherited by all ServerSessions created from it.

Threads will now be awakened when the objects they're waiting on are signaled, instead of repeating the WaitSynchronization call every now and then.

The scheduler is now called once after every SVC call, and once after a thread is awakened from sleep by its timeout callback.

This new implementation is based off reverse-engineering of the real kernel.

See https://gist.github.com/Subv/02f29bd9f1e5deb7aceea1e8f019c8f4 for a more detailed description of how the real kernel handles rescheduling.

Sessions and Ports are now detached from each other.
HLE services are handled by means of a SessionRequestHandler class, Interface now inherits from this class.
The File and Directory classes are no longer kernel objects, but SessionRequestHandlers instead, bound to a ServerSession when requested.
File::OpenLinkFile now creates a new session pair and binds the File instance to it.

Pass the triggering ServerSession to the HLE command handler to differentiate which session caused the request.

Kernel/HLE: Service::Interface no longer inherits from any Kernel object, and is now its own standalone class.

Interface is now used by aggregation in ClientPort, to forward service commands to their HLE implementation if needed.