[log] Fix logging for tests (grpc#37560)

This will fix timestamps on logs and show all `VLOG(2)` logs on tests by default.

Currently, timestamps on logs are shown as -
```
I0000 00:00:1724385276.681936 1894892 config.cc:262] gRPC experiments enabled: call_tracer_in_transport, event_engine_dns, event_engine_listener, monitoring_experiment, pick_first_new, trace_record_callops, work_serializer_clears_time_cache
```
After invoking `absl::InitializeLog()`, this gets fixed to -
```
I0823 03:55:53.993928 1895644 config.cc:262] gRPC experiments enabled: call_tracer_in_transport, event_engine_dns, event_engine_listener, monitoring_experiment, pick_first_new, trace_record_callops, work_serializer_clears_time_cache
```

Closes grpc#37560

COPYBARA_INTEGRATE_REVIEW=grpc#37560 from yashykt:ImproveLoggingForTests 6643333
PiperOrigin-RevId: 666956421

test/core/test_util/BUILD

@@ -121,6 +121,7 @@ grpc_cc_library(
         "absl/debugging:failure_signal_handler",
         "absl/log:check",
         "absl/log:globals",
+        "absl/log:initialize",
         "absl/log:log",
         "absl/status",
         "absl/status:statusor",
@@ -168,6 +169,7 @@ grpc_cc_library(
     external_deps = [
         "absl/debugging:failure_signal_handler",
         "absl/log:check",
+        "absl/log:initialize",
         "absl/log:log",
         "absl/status",
         "absl/status:statusor",

test/core/test_util/test_config.cc

@@ -21,8 +21,11 @@
 #include <inttypes.h>
 #include <stdlib.h>
 
+#include <mutex>
+
 #include "absl/debugging/failure_signal_handler.h"
 #include "absl/log/globals.h"
+#include "absl/log/initialize.h"
 #include "absl/log/log.h"
 #include "absl/status/status.h"
 #include "absl/strings/match.h"
@@ -120,9 +123,20 @@ void ParseTestArgs(int* argc, char** argv) {
     ++i;
   }
 }
+
+// grpc-oss-only-begin
+std::once_flag log_flag;
+// grpc-oss-only-end
+
 }  // namespace
 
 void grpc_test_init(int* argc, char** argv) {
+  // grpc-oss-only-begin
+  std::call_once(log_flag, []() { absl::InitializeLog(); });
+  absl::SetGlobalVLogLevel(2);
+  absl::SetMinLogLevel(absl::LogSeverityAtLeast::kInfo);
+  absl::SetStderrThreshold(absl::LogSeverityAtLeast::kInfo);
+  // grpc-oss-only-end
   gpr_log_verbosity_init();
   ParseTestArgs(argc, argv);
   grpc_core::testing::InitializeStackTracer(argv[0]);