Kernel: Add jail semantics to methods iterating over thread lists

We should consider whether the selected Thread is within the same jail
or not.
Therefore let's make it clear to callers with jail semantics if a called
method checks if the desired Thread object is within the same jail.

As for Thread::for_each_* methods, currently nothing in the kernel
codebase needs iteration with consideration for jails, so the old
Thread::for_each* were simply renamed to include "ignoring_jails" suffix
in their names.

Kernel/Tasks/Process.cpp

@@ -952,7 +952,7 @@ ErrorOr<void> Process::send_signal(u8 signal, Process* sender)
 {
     VERIFY(is_user_process());
     // Try to send it to the "obvious" main thread:
-    auto receiver_thread = Thread::from_tid(pid().value());
+    auto receiver_thread = Thread::from_tid_in_same_jail(pid().value());
     // If the main thread has died, there may still be other threads:
     if (!receiver_thread) {
         // The first one should be good enough.