[rtc_tools/video_encoder] Support Y4M file input

This CL adds `Y4mFrameGenerator` to support Y4M file input.

Bug: webrtc:15210
Change-Id: If21e40a609b3c6f980a413fb183cd4dfb5123aab
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/311520
Commit-Queue: Jianhui J Dai <jianhui.j.dai@intel.com>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#40460}
diff --git a/rtc_tools/BUILD.gn b/rtc_tools/BUILD.gn
index 517a739..5ead8a0 100644
--- a/rtc_tools/BUILD.gn
+++ b/rtc_tools/BUILD.gn
@@ -444,6 +444,7 @@
       "//modules/video_coding/codecs/av1:av1_svc_config",
       "//modules/video_coding/svc:scalability_mode_util",
       "//rtc_base:logging",
+      "//test:y4m_frame_generator",
       "//third_party/abseil-cpp/absl/flags:flag",
       "//third_party/abseil-cpp/absl/flags:parse",
       "//third_party/abseil-cpp/absl/flags:usage",