test_runner: capture process state in entry point instead of runner

Move process.* reads (process.argv, process.env, process.cwd) from
runner.js to the CLI entry point (main/test_runner.js), so that runner.js
can be loaded without side effects in snapshot environments.

The execArgv case is handled via a fallback in getRunArgs(): when no
execArgv is passed in options, process.execArgv is still read directly
to propagate V8-only flags to child processes.

PR-URL: https://github.com/nodejs/node/pull/XXXXX
Refs: #56131

Author: Krsna Suraj

lib/internal/main/test_runner.js

@@ -31,6 +31,8 @@ if (isUsingInspector() && options.isolation === 'process') {
 }
 
 options.globPatterns = ArrayPrototypeSlice(process.argv, 1);
+options.env = process.env;
+options.cwd = process.cwd();
 
 debug('test runner configuration:', options);
 run(options).on('test:summary', (data) => {

lib/internal/test_runner/runner.js

@@ -206,8 +206,9 @@ function getRunArgs(path, { forceExit,
    * An example of such option are --allow-natives-syntax and --expose-gc
    */
   const nodeOptionsSet = new SafeSet(processNodeOptions);
+  const sourceExecArgv = execArgv.length > 0 ? execArgv : process.execArgv;
   const unknownProcessExecArgv = ArrayPrototypeFilter(
-    process.execArgv,
+    sourceExecArgv,
     (arg, i, arr) => !nodeOptionsSet.has(arg) && filterExecArgv(arg, i, arr),
   );
   ArrayPrototypePushApply(runArgs, unknownProcessExecArgv);
@@ -500,7 +501,7 @@ function runTestFile(path, filesWatcher, opts) {
   const subtest = opts.root.createSubtest(FileTest, testPath, testOpts, async (t) => {
     const args = getRunArgs(path, opts);
     const stdio = ['pipe', 'pipe', 'pipe'];
-    const env = { __proto__: null, NODE_TEST_CONTEXT: 'child-v8', ...(opts.env || process.env) };
+    const env = { __proto__: null, NODE_TEST_CONTEXT: 'child-v8', ...(opts.env ?? {}) };
 
     // Acquire a worker ID from the pool for process isolation mode
     let workerId;
@@ -733,7 +734,7 @@ function run(options = kEmptyObject) {
     argv = [],
     cwd = process.cwd(),
     rerunFailuresFilePath,
-    env,
+    env = process.env,
   } = options;
 
   if (files != null) {
@@ -909,7 +910,7 @@ function run(options = kEmptyObject) {
     validatePath(globalSetupPath, 'options.globalSetupPath');
   }
 
-  if (env != null) {
+  if ('env' in options) {
     validateObject(env, 'options.env');
 
     if (isolation === 'none') {
@@ -1000,7 +1001,7 @@ function run(options = kEmptyObject) {
   };
 
   if (isolation === 'process') {
-    if (process.env.NODE_TEST_CONTEXT !== undefined) {
+    if ((env?.NODE_TEST_CONTEXT ?? process.env.NODE_TEST_CONTEXT) !== undefined) {
       process.emitWarning('node:test run() is being called recursively within a test file. skipping running files.');
       root.postRun();
       return root.reporter;