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);
```

core/shared/platform/include/platform_api_vmcore.h

@@ -142,6 +142,24 @@ os_munmap(void *addr, size_t size);
 int
 os_mprotect(void *addr, size_t size, int prot);
 
+static inline void *
+os_mremap_slow(void *old_addr, size_t old_size, size_t new_size)
+{
+    void *new_memory = os_mmap(NULL, new_size, MMAP_PROT_WRITE | MMAP_PROT_READ,
+                               0, os_get_invalid_handle());
+    if (!new_memory) {
+        return NULL;
+    }
+    /*
+     * bh_memcpy_s can't be used as it doesn't support values bigger than
+     * UINT32_MAX
+     */
+    memcpy(new_memory, old_addr, new_size < old_size ? new_size : old_size);
+    os_munmap(old_addr, old_size);
+
+    return new_memory;
+}
+
 /* Doesn't guarantee that protection flags will be preserved.
    os_mprotect() must be called after remapping. */
 void *