AK+Kernel: Help the compiler inline a bunch of trivial methods

If these methods get inlined, the compiler is able to statically eliminate most
of the assertions. Alas, it doesn't realize this, and believes inlining them to
be too expensive. So give it a strong hint that it's not the case.

This *decreases* the kernel binary size.

Kernel/Thread.cpp

@@ -384,11 +384,6 @@ void Thread::send_urgent_signal_to_self(u8 signal)
     (void)block<SemiPermanentBlocker>(SemiPermanentBlocker::Reason::Signal);
 }
 
-bool Thread::has_unmasked_pending_signals() const
-{
-    return m_pending_signals & ~m_signal_mask;
-}
-
 ShouldUnblockThread Thread::dispatch_one_pending_signal()
 {
     ASSERT_INTERRUPTS_DISABLED();