[experiments] Make output more diffable/readable (#30807)

* [experiments] Make output more diffable/readable

* Automated change: Fix sanity tests

* buildifier sized indentations

Co-authored-by: ctiller <ctiller@users.noreply.github.com>

bazel/experiments.bzl

@@ -15,4 +15,12 @@
 # Automatically generated by tools/codegen/core/gen_experiments.py
 
 """Dictionary of tags to experiments so we know when to test different experiments."""
-EXPERIMENTS = {"endpoint_test": ["tcp_frame_size_tuning"], "core_end2end_test": ["tcp_frame_size_tuning"]}
+
+EXPERIMENTS = {
+    "core_end2end_test": [
+        "tcp_frame_size_tuning",
+    ],
+    "endpoint_test": [
+        "tcp_frame_size_tuning",
+    ],
+}

tools/codegen/core/gen_experiments.py

@@ -91,7 +91,10 @@ def snake_to_pascal(s):
 def put_banner(files, banner, prefix):
     for f in files:
         for line in banner:
-            print('%s %s' % (prefix, line), file=f)
+            if not line:
+                print(prefix, file=f)
+            else:
+                print('%s %s' % (prefix, line), file=f)
         print(file=f)
 
 
@@ -215,4 +218,11 @@ with open('bazel/experiments.bzl', 'w') as B:
         "\"\"\"Dictionary of tags to experiments so we know when to test different experiments.\"\"\"",
         file=B)
 
-    print("EXPERIMENTS=%r" % dict(tags_to_experiments), file=B)
+    print(file=B)
+    print("EXPERIMENTS = {", file=B)
+    for tag, experiments in sorted(tags_to_experiments.items()):
+        print("    \"%s\": [" % tag, file=B)
+        for experiment in sorted(experiments):
+            print("        \"%s\"," % experiment, file=B)
+        print("    ],", file=B)
+    print("}", file=B)