StressTest: add --io_prov_buffs_use_dynamic

Summary:
Add `--io_prov_buffs_use_dynamic` to the thrift stresstest and map it to
`IoUringProvidedBufferRingMode::Dynamic`. Add a fastio stresstest config that
enables the option for both the server and client.

Also declare `IoUringBufferProvider` in `AsyncIoUringSocket.h`, which is needed
to build the stresstest against the buffer-provider selector commit.

Reviewed By: jlhe97

Differential Revision: D116735817

fbshipit-source-id: 62ad14d2d0e1a0db5a3382b1f618957070a66bae

Author: spikeh

third-party/thrift/src/thrift/conformance/stresstest/util/IoUringUtil.cpp

@@ -59,6 +59,10 @@ DEFINE_bool(
     io_prov_buffs_use_incremental,
     false,
     "Enable the use of incremental buffers usage for recv operations. false by default.");
+DEFINE_bool(
+    io_prov_buffs_use_dynamic,
+    false,
+    "Use the dynamic io_uring provided buffer ring. Off by default.");
 #if FOLLY_HAS_LIBURING
 
 namespace apache::thrift::stress {
@@ -140,6 +144,11 @@ void setIoUringCommonOptionsFromFlags(folly::IoUringOptions& options) {
   if (FLAGS_io_prov_buffs_use_incremental) {
     options.setEnableIncrementalBuffers(true);
   }
+
+  if (FLAGS_io_prov_buffs_use_dynamic) {
+    options.setProvidedBufferRingMode(
+        folly::IoUringOptions::ProvidedBufferRingMode::Dynamic);
+  }
 }
 
 folly::IoUringBackend::Options getIoUringOptions() {