Refactor fuzzer transform generation

Also splits out various utility classes from tint_common_fuzzer and
uses consistent naming for utility classes.

BUG=tint:1106

Change-Id: Ic343741eea799366850c46834865d50885554a84
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/65301
Auto-Submit: Ryan Harrison <rharrison@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>
Commit-Queue: Ryan Harrison <rharrison@chromium.org>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>

fuzzers/fuzzer_init.cc

@@ -0,0 +1,35 @@
+// Copyright 2021 The Tint Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "fuzzers/fuzzer_init.h"
+#include "fuzzers/cli.h"
+
+namespace tint {
+namespace fuzzers {
+
+namespace {
+CliParams cli_params;
+}
+
+const CliParams& GetCliParams() {
+  return cli_params;
+}
+
+extern "C" int LLVMFuzzerInitialize(int* argc, char*** argv) {
+  cli_params = ParseCliParams(argc, *argv);
+  return 0;
+}
+
+}  // namespace fuzzers
+}  // namespace tint