Use mimalloc for Ladybird-owned allocations without overriding malloc().
Route kmalloc(), kcalloc(), krealloc(), and kfree() through mimalloc,
and put the embedded Rust crates on the same allocator via a shared
shim in AK/kmalloc.cpp.
This also lets us drop kfree_sized(), since it no longer used its size
argument. StringData, Utf16StringData, JS object storage, Rust error
strings, and the CoreAudio playback helpers can all free their AK-backed
storage with plain kfree().
Sanitizer builds still use the system allocator. LeakSanitizer does not
reliably trace references stored in mimalloc-managed AK containers, so
static caches and other long-lived roots can look leaked. Pass the old
size into the Rust realloc shim so aligned fallback reallocations can
move posix_memalign-backed blocks safely.
Static builds still need a little linker help. macOS app binaries need
the Rust allocator entry points forced in from liblagom-ak.a, while
static ELF links can pull in identical allocator shim definitions from
multiple Rust staticlibs. Keep the Apple -u flags and allow those
duplicate shim symbols for LibJS and LibRegex links on Linux and BSD.
These changes are compatible with clang-format 16 and will be mandatory
when we eventually bump clang-format version. So, since there are no
real downsides, let's commit them now.
This fixes a build issue introduced in 23d66fe, where the compiler
statically detected that that mismatching new and delete operators were
used.
Clang generates a warning for this, for the reasons described in the
comment in `AK/kmalloc.cpp`, but GCC does not.
Besides moving the allocator functions into a `.cpp` file, declarations
in `AK/kmalloc.cpp` were reordered to have imports at the top, in order
to make the code more readable.
Cooperate with the compiler to generate and execute the _init_array list
of constructor functions on userspace program statup. This took two days
to get working, my goodness. :^)
