shared-platform: Remove dependency on shared-utils' bh_memory_remap_slow (#3153)

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);
```

product-mini/platforms/nuttx/wamr.mk

@@ -437,7 +437,6 @@ CSRCS += nuttx_platform.c \
          bh_hashmap.c \
          bh_list.c \
          bh_log.c \
-         bh_memutils.c \
          bh_queue.c \
          bh_vector.c \
          bh_read_file.c \