[build] Shard tests a little more (#30489)

* [build] Shard tests a little more

* Automated change: Fix sanity tests

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

test/core/transport/chttp2/BUILD

@@ -225,6 +225,7 @@ grpc_cc_test(
     timeout = "long",  # Required for internal test infrastructure (cl/325757166)
     srcs = ["too_many_pings_test.cc"],
     external_deps = ["gtest"],
+    shard_count = 7,
     deps = [
         "//:gpr",
         "//:grpc",

test/cpp/end2end/xds/BUILD

@@ -155,7 +155,7 @@ grpc_cc_test(
     ],
     flaky = True,  # TODO(b/144705388)
     linkstatic = True,  # Fixes dyld error on MacOS
-    shard_count = 10,
+    shard_count = 20,
     tags = [
         "no_test_ios",
         "no_windows",
@@ -203,6 +203,7 @@ grpc_cc_test(
         "gtest",
     ],
     linkstatic = True,  # Fixes dyld error on MacOS
+    shard_count = 15,
     tags = [
         "no_test_ios",
         "no_windows",
@@ -250,6 +251,7 @@ grpc_cc_test(
         "gtest",
     ],
     linkstatic = True,  # Fixes dyld error on MacOS
+    shard_count = 5,
     tags = [
         "no_test_ios",
         "no_windows",
@@ -300,6 +302,7 @@ grpc_cc_test(
     ],
     flaky = True,  # TODO(b/144705388)
     linkstatic = True,  # Fixes dyld error on MacOS
+    shard_count = 10,
     tags = [
         "no_test_ios",
         "no_windows",