Revert "Make the test library for field trials testonly."

This reverts commit c33f1a828c31412e7422e7bf11db7c9b61fab339.

Reason for revert: Breaks downstream project.

Original change's description:
> Make the test library for field trials testonly.
>
> Bug: None
> Change-Id: I703a82e0ca10908bdc56c0d4f1455e042ce74ac1
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/267163
> Reviewed-by: Artem Titov <titovartem@webrtc.org>
> Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
> Cr-Commit-Position: refs/heads/main@{#37371}

Bug: None
Change-Id: I1d6d88ed9f32d5f1aab3159bbd1f279f164a079d
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/267164
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Bot-Commit: rubber-stamper@appspot.gserviceaccount.com <rubber-stamper@appspot.gserviceaccount.com>
Owners-Override: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#37372}
diff --git a/rtc_tools/BUILD.gn b/rtc_tools/BUILD.gn
index b1bcbe1..1a56be8 100644
--- a/rtc_tools/BUILD.gn
+++ b/rtc_tools/BUILD.gn
@@ -357,7 +357,6 @@
     }
 
     rtc_library("event_log_visualizer_utils") {
-      testonly = true
       visibility = [ "*" ]
       sources = [
         "rtc_event_log_visualizer/alerts.cc",
diff --git a/test/BUILD.gn b/test/BUILD.gn
index 5f2cc58..4e41076 100644
--- a/test/BUILD.gn
+++ b/test/BUILD.gn
@@ -215,7 +215,6 @@
 }
 
 rtc_library("field_trial") {
-  testonly = true
   visibility = [ "*" ]
   sources = [
     "field_trial.cc",
@@ -230,7 +229,6 @@
 }
 
 rtc_library("explicit_key_value_config") {
-  testonly = true
   sources = [
     "explicit_key_value_config.cc",
     "explicit_key_value_config.h",
@@ -245,7 +243,6 @@
 }
 
 rtc_library("scoped_key_value_config") {
-  testonly = true
   visibility = [ "*" ]
   sources = [
     "scoped_key_value_config.cc",