[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/libraries/cpu/include/cpu/features.inc

@@ -13,6 +13,7 @@ CPU_FEATURE_REQ(pat,        0x00000001, 0, edx, 16)
 CPU_FEATURE_REQ(fxsr,       0x00000001, 0, edx, 24)
 
 CPU_FEATURE_OPT(fsgsbase,   0x00000007, 0, ebx,  0)
+CPU_FEATURE_OPT(bmi1,       0x00000007, 0, ebx,  3)
 CPU_FEATURE_OPT(invpcid,    0x00000007, 0, ebx, 10)
 
 CPU_FEATURE_OPT(pku,        0x00000007, 0, ecx,  3)