[boot][kernel] Replace frame allocator with bitmap-based one

The previous frame allocator involved a lot of splitting and merging
linked lists and lost all information about frames while they were
allocated. The new allocator is based on an array of descriptor
structures and a bitmap. Each memory map region of allocatable memory
becomes one or more descriptors, each mapping up to 1GiB of physical
memory. The descriptors implement two levels of a bitmap tree, and have
a pointer into the large contiguous bitmap to track individual pages.

src/boot/loader.cpp

@@ -27,7 +27,7 @@ load_file(
 	fs::file file = disk.open(path);
 	buffer b = file.load(type);
 
-	console::print(L"    Loaded at: 0x%lx, %d bytes\r\n", b.data, b.size);
+	//console::print(L"    Loaded at: 0x%lx, %d bytes\r\n", b.data, b.size);
 	return b;
 }