[k2] fix coro frame alignment

[PetrShumilov]

With clang-18 and -O2 member initialization of record types may be lowered to SIMD instructions. For example, member zero initialization for promise_base (part of coroutine frame) may looks like:

;   void* m_next{};
  2bcb84: c5 f8 57 c0                  	vxorps	%xmm0, %xmm0, %xmm0
  2bcb88: c5 f8 29 43 50               	vmovaps	%xmm0, 0x50(%rbx)
  2bcb8d: c5 f8 29 43 40               	vmovaps	%xmm0, 0x40(%rbx)

According to the x86 specification, the destination operand of vmovaps must be aligned to 16, 32, or 64 bytes, depending on the register width. However,

• the implementation of memory manager which is used for allocation of coroutine frame doesn't get any guarantees about alignment;
• by default, without passing -fcoro-aligned-allocation option, clang doesn't invoke overload of operator new with alignment parameter;
• such program:

<?php
/**
 * @kphp-required
 * @param int $a
 * @param int $b
 * @return int
 */
function cmp(int $a, int $b) {
  sched_yield();
  return $b - $a;
}
function main() {
  $arr = [3, 2, 1];
  uasort($arr, 'cmp');
}
main();

is failed with SIGSEGV when -O2 is enabled.