Use new test framework in toolchain to reduce per-test overhead (#2821)

This builds on #2814 by adding the test framework to the toolchain. On Linux, this is 7s -> 4s for me. #2811 has more detailed timing for the explorer, which also had more dramatic changes because it's about 3x more tests run in 2x as many ways (6x total).

Co-authored-by: Chandler Carruth <chandlerc@gmail.com>

toolchain/parser/parse_tree_file_test.cpp

@@ -0,0 +1,37 @@
+// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+// Exceptions. See /LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+
+#include <vector>
+
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Support/raw_ostream.h"
+#include "testing/file_test/file_test_base.h"
+#include "toolchain/driver/driver.h"
+
+namespace Carbon::Testing {
+namespace {
+
+class ParserFileTest : public FileTestBase {
+ public:
+  explicit ParserFileTest(llvm::StringRef path) : FileTestBase(path) {}
+
+  auto RunOverFile(llvm::raw_ostream& stdout, llvm::raw_ostream& stderr)
+      -> bool override {
+    Driver driver(stdout, stderr);
+    return driver.RunFullCommand({"dump", "parse-tree", path()});
+  }
+};
+
+}  // namespace
+
+auto RegisterFileTests(const std::vector<llvm::StringRef>& paths) -> void {
+  ParserFileTest::RegisterTests(
+      "ParserFileTest", paths,
+      [](llvm::StringRef path) { return new ParserFileTest(path); });
+}
+
+}  // namespace Carbon::Testing