[kernel] Remove explicit allocator passing

Many kernel objects had to keep a hold of refrences to allocators in
order to pass them on down the call chain. Remove those explicit
refrences and use `operator new`, `operator delete`, and define new
`kalloc` and `kfree`.

Also remove `slab_allocator` and replace it with a new mixin for slab
allocation, `slab_allocated`, that overrides `operator new` and
`operator free` for its subclass.

Remove some no longer used related headers, `buddy_allocator.h` and
`address_manager.h`

Tags: memory

src/libraries/initrd/include/initrd/initrd.h

@@ -49,7 +49,7 @@ class disk
 public:
 	/// Constructor.
 	/// \arg start  The start of the initrd in memory
-	disk(const void *start, kutil::allocator &alloc);
+	disk(const void *start);
 
 	/// Get the vector of files on the disk
 	const kutil::vector<file> & files() const { return m_files; }

src/libraries/initrd/initrd.cpp

@@ -23,8 +23,7 @@ file::executable() const {
 }
 
 
-disk::disk(const void *start, kutil::allocator &alloc) :
-	m_files(alloc)
+disk::disk(const void *start)
 {
 	auto *header = reinterpret_cast<const disk_header *>(start);
 	size_t length = header->length;