[uart] Add first pass UART driver and logger

First attempt at a UART driver. I'm not sure it's the most stable. Now
that userspace is handling displaying logs, also removed serial and log
output support from the kernel.

src/kernel/apic.cpp

@@ -3,7 +3,7 @@
 #include "clock.h"
 #include "interrupts.h"
 #include "io.h"
-#include "log.h"
+#include "logger.h"
 #include "memory.h"
 
 uint64_t lapic::s_ticks_per_us = 0;