test: replace benchmark test with vitest bench script

Use vitest bench for proper statistical benchmarking instead of a test.
Run with: npx vitest bench

Results on synthetic monorepo (500+ files):
  targeted: 2.12ms (471 ops/s)
  eager:    99.3ms (10 ops/s)
  46.83x faster

Author: Alp

tests/benchmark.bench.ts

@@ -0,0 +1,42 @@
+import * as path from 'node:path';
+import {Project} from 'ts-morph';
+import {bench, describe} from 'vitest';
+import {
+  addSourceFilesFromTsConfigSafe,
+  ensureSourceFileInProject,
+} from '../src/cli/ts-project';
+import {discoverAllTsConfigs} from '../src/cli/tsconfig';
+
+const fixtureRoot = path.resolve(
+  __dirname,
+  'benchmarks/synthetic-monorepo/tsconfig.json',
+);
+const schemaConfigFile = path.resolve(
+  __dirname,
+  'benchmarks/synthetic-monorepo/schema/drizzle-zero.config.ts',
+);
+
+describe('file loading', () => {
+  bench('eager: load all files from all tsconfigs', async () => {
+    const allTsConfigPaths = await discoverAllTsConfigs(fixtureRoot);
+    const project = new Project({
+      tsConfigFilePath: fixtureRoot,
+      skipAddingFilesFromTsConfig: true,
+    });
+    for (const tsConfigPath of allTsConfigPaths) {
+      addSourceFilesFromTsConfigSafe({tsProject: project, tsConfigPath});
+    }
+  });
+
+  bench('targeted: load only the requested file', async () => {
+    const project = new Project({
+      tsConfigFilePath: fixtureRoot,
+      skipAddingFilesFromTsConfig: true,
+    });
+    ensureSourceFileInProject({
+      tsProject: project,
+      filePath: schemaConfigFile,
+      debug: false,
+    });
+  });
+});