fix: Flush buffers before renaming cache file (#2927)

If clio shuts itself down due to exceeding graceful period when cache is
saved and renamed but the buffers are not flushed, we may end up with a
corrupted cache file. Clio will detect corruption and will not load
corrupted cache file, but we could avoid it by explicitly flushing
ofstream buffer.

src/data/impl/LedgerCacheFile.cpp

@@ -115,6 +115,11 @@ LedgerCacheFile::write(DataView dataView)
     auto const hash = file.hash();
     file.write(hash.data(), decltype(hash)::bytes);
 
+    // flush internal buffer explicitly before renaming
+    if (auto const expectedSuccess = file.close(); not expectedSuccess.has_value()) {
+        return expectedSuccess;
+    }
+
     try {
         std::filesystem::rename(newFilePath, path_);
     } catch (std::exception const& e) {