As an original design rule, the code in `core/shared/platform` should not
rely on the code in `core/share/utils`. In the current implementation,
platform layer calls function `bh_memory_remap_slow` in utils layer.
This PR adds inline function `os_mremap_slow` in platform_api_vmcore.h,
and lets os_remap call it if mremap fails. And remove bh_memutils.h/c as
as they are unused.
And resolve the compilation warning in wamrc:
```bash
core/shared/platform/common/posix/posix_memmap.c:255:16:
warning: implicit declaration of function ‘bh_memory_remap_slow’
255 | return bh_memory_remap_slow(old_addr, old_size, new_size);
```
b6adec373e