Replace gflags usages with rtc_base/flags in all targets based on test_main

webrtc/modules/audio_coding/BUILD.gn

Index: webrtc/modules/audio_coding/BUILD.gn
diff --git a/webrtc/modules/audio_coding/BUILD.gn b/webrtc/modules/audio_coding/BUILD.gn
index 3e6a1834868daa33c7d2f9f2bf3d8460d665e4df..9b68f41cfa3eefff07c4ea8319a2deef41f87cb6 100644
--- a/webrtc/modules/audio_coding/BUILD.gn
+++ b/webrtc/modules/audio_coding/BUILD.gn
@@ -1658,7 +1658,6 @@ if (rtc_include_tests) {
       "../../rtc_base:rtc_base_approved",
       "../../test:test_support",
       "//testing/gtest",
-      "//third_party/gflags",
     ]
   }
 
@@ -1844,9 +1843,9 @@ if (rtc_include_tests) {
       ":neteq_quality_test_support",
       ":neteq_tools",
       ":webrtc_opus",
+      "../../rtc_base:rtc_base_approved",
       "../../test:test_main",
       "//testing/gtest",
-      "//third_party/gflags",
     ]
   }
 
@@ -1884,7 +1883,6 @@ if (rtc_include_tests) {
       "../../system_wrappers:system_wrappers_default",
       "../../test:test_main",
       "//testing/gtest",
-      "//third_party/gflags",
     ]
   }
 
@@ -1902,7 +1900,6 @@ if (rtc_include_tests) {
       "../../rtc_base:rtc_base_approved",
       "../../test:test_main",
       "//testing/gtest",
-      "//third_party/gflags",
     ]
   }
 
@@ -1920,7 +1917,6 @@ if (rtc_include_tests) {
       "../../rtc_base:rtc_base_approved",
       "../../test:test_main",
       "//testing/gtest",
-      "//third_party/gflags",
     ]
   }
 
@@ -2207,7 +2203,6 @@ if (rtc_include_tests) {
       "../../test:test_support",
       "//testing/gmock",
       "//testing/gtest",
-      "//third_party/gflags",
     ]
 
     defines = audio_coding_defines