kernel/process: Decouple TLS handling from threads

Extracts out all of the thread local storage management from thread
instances themselves and makes the owning process handle the management
of the memory. This brings the memory management slightly more in line
with how the kernel handles these allocations.

Furthermore, this also makes the TLS page management a little more
readable compared to the lingering implementation that was carried over
from Citra.

src/core/hle/kernel/thread.cpp

@@ -65,7 +65,7 @@ void Thread::Stop() {
     owner_process->UnregisterThread(this);
 
     // Mark the TLS slot in the thread's page as free.
-    owner_process->FreeTLSSlot(tls_address);
+    owner_process->FreeTLSRegion(tls_address);
 }
 
 void Thread::WakeAfterDelay(s64 nanoseconds) {
@@ -205,9 +205,9 @@ ResultVal<SharedPtr<Thread>> Thread::Create(KernelCore& kernel, std::string name
     thread->name = std::move(name);
     thread->callback_handle = kernel.ThreadWakeupCallbackHandleTable().Create(thread).Unwrap();
     thread->owner_process = &owner_process;
+    thread->tls_address = thread->owner_process->CreateTLSRegion();
     thread->scheduler = &system.Scheduler(processor_id);
     thread->scheduler->AddThread(thread);
-    thread->tls_address = thread->owner_process->MarkNextAvailableTLSSlotAsUsed(*thread);
 
     thread->owner_process->RegisterThread(thread.get());