doc: add detailed explanation of suites and their behavior in the test runner

[algowizzz]

Summary

This PR adds a dedicated Suites section to the node:test documentation.
The existing docs reference suites (for example, in the Subtests section) without explaining what they are or how they differ from tests with subtests. This addition fills that gap and clarifies suite behavior.

What This PR Adds

• A new “Suites” section covering:
  • What a suite is and how it works
  • Synchronous callback behavior when registering tests
  • How suites wait for all nested tests/suites
  • How suite results depend entirely on their children
• Examples of suites and nested suites
• A comparison table between suites (suite() / describe()) and subtests (t.test())
• Clarification that describe() is an alias of suite()

Why This Is Needed

• The documentation references suites without defining them.
• Developers transitioning from Mocha/Jest often assume different semantics.
• Suites and subtests look similar but behave differently in important ways (async behavior, execution order, cancellation).
• This makes the test runner easier to understand and reduces confusion.

Related Issue

Fixes: #60758

[nodejs-github-bot]

Review requested:

• @nodejs/test_runner

[Ethan-Arrowood]

good start.

[Ethan-Arrowood]

looking good. I'd like this to get some more input from other test_runner maintainers too.

[Ethan-Arrowood]

Suggested change

	**Suites vs. Subtests**
	### Suites vs. Subtests

[Ethan-Arrowood]

Suggested change

	to register nested tests or nested suites.
	to register lifecycle methods (such as `before()` and `after()`), nested tests, or nested suites.

[Ethan-Arrowood]

Suggested change

	tests and suites inside it --- suites cannot fail independently.
	tests and suites inside it - suites cannot fail independently.

[Ethan-Arrowood]

Lets simplify this example to demonstrate everything in one code block.

Suggested change

	``` js
	import { suite, test } from 'node:test';
	import assert from 'node:assert';
	suite('math operations', () => {
	test('addition', () => {
	assert.strictEqual(1 + 1, 2);
	});
	test('multiplication', () => {
	assert.strictEqual(2 * 2, 4);
	});
	});
	```
	``` js
	suite('user features', () => {
	suite('profile', () => {
	test('updates display name', () => {
	assert.ok(true);
	});
	});
	suite('settings', () => {
	test('enables notifications', () => {
	assert.ok(true);
	});
	});
	});
	```
	```js
	import { suite, test } from 'node:test';
	import assert from 'node:assert';
	suite('math operations', () => {
	test('addition', () => {
	assert.strictEqual(1 + 1, 2);
	});
	suite('multiplication', () => {
	test('negative one', () => {
	assert.strictEqual(2 * -1, -2);
	});
	test('zero', () => {
	assert.strictEqual(2 * 0, 0);
	});
	});
	});
	```

[Ethan-Arrowood]

What is another way to cancel the parent suite and the subtests continue to execute?

[Ethan-Arrowood]

Suggested change

	*Suite example*
	### Suite example

[Ethan-Arrowood]

Suggested change

	*Subtest example*
	### Subtest example