Refactor POSIX function usage in file_cache

This commit changes the way POSIX functions are called in the file_cache module. Instead of importing the functions directly from libc, they are now referred to via the libc namespace. This improves code clarity by making it clear where these functions originate from.

crates/rooch-common/src/fs/file_cache.rs

@@ -1,7 +1,6 @@
 // Copyright (c) RoochNetwork
 // SPDX-License-Identifier: Apache-2.0
 
-use libc::{posix_fadvise, POSIX_FADV_DONTNEED};
 use std::fs::File;
 use std::io::{Error, Result};
 use std::os::unix::io::AsRawFd;
@@ -23,11 +22,11 @@ impl FileCacheManager {
     pub fn drop_cache_range(&self, offset: u64, len: u64) -> Result<()> {
         let fd = self.file.as_raw_fd();
         let ret = unsafe {
-            posix_fadvise(
+            libc::posix_fadvise(
                 fd,
                 offset as libc::off_t,
                 len as libc::off_t,
-                POSIX_FADV_DONTNEED,
+                libc::POSIX_FADV_DONTNEED,
             )
         };