Add support for multiple inflight files and one shot hash small files

The IO Ring now supports bashing multiple submissions and can handle
multiple files at the same time.

Hashing small files using XXH3_128bits() instead of the streaming
pipeline(XXH3_128bits_reset(), XXH3_128bits_update(),
XXH3_128bits_digest()), this reduses the overhead of creating a state
and digest, coupled with the IO Ring it improves the hashing of small
files whose size is inferior to the size of IO Ring buffers

file_hasher.c

@@ -87,7 +87,7 @@ int main(int argc, char **argv) {
   printf("  Selected instruction set: %s\n", get_xxhash_instruction_set());
 
   // Align IO Ring block size to the system page size
-  u64 g_ioring_read_block = ALIGN_UP_POW2(IORING_READ_BLOCK, g_pagesize);
+  g_ioring_buffer_size = ALIGN_UP_POW2(IORING_BUFFER_SIZE, g_pagesize);
   // -------------------------------
   // Scanning and hashing
   // -------------------------------
@@ -120,6 +120,7 @@ int main(int argc, char **argv) {
 
   // Starting hash threads
   size_t num_hash_threads = num_threads;
+  // size_t num_hash_threads = 1;
 
   WorkerContext workers[num_hash_threads];
   Thread *hash_threads =