feat(checker): add runtime fatal-error prevention check

[faisalahammad]

Summary

Adds a new static check Runtime_Fatal_Error_Prevention_Check and corresponding PHPCS sniff RuntimeFatalErrorPreventionSniff to analyze plugins for high-risk coding patterns that commonly trigger runtime fatal errors. These include unguarded imports, direct/unguarded class instantiations or function calls of optional components, dynamic callback definitions that might be missing, and incorrect class method hook attachments.

Fixes #1273

Changes

phpcs-rulesets/plugin-check.ruleset.xml

Before:

	<!-- Prohibit the use of the `goto` PHP language construct. -->
	<rule ref="Generic.PHP.DiscourageGoto.Found">

After:

	<!-- Prevent runtime fatal errors. -->
	<rule ref="PluginCheck.CodeAnalysis.RuntimeFatalErrorPrevention"/>

	<!-- Prohibit the use of the `goto` PHP language construct. -->
	<rule ref="Generic.PHP.DiscourageGoto.Found">

Why: Registers the new custom PHPCS sniff under the core plugin-check ruleset to run as part of the PHPCS static checks.

includes/Checker/Default_Check_Repository.php

Before:

				\'wp_functions_compatibility\' => new Checks\\Plugin_Repo\\WP_Functions_Compatibility_Check(),
			)
		);

After:

				\'wp_functions_compatibility\'     => new Checks\\Plugin_Repo\\WP_Functions_Compatibility_Check(),
				\'runtime_fatal_error_prevention\' => new Checks\\Plugin_Repo\\Runtime_Fatal_Error_Prevention_Check(),
			)
		);

Why: Registers the new Runtime_Fatal_Error_Prevention_Check static check class into the default check repository so it gets run automatically during plugin checks.

Testing

Test 1: Run Sniff Unit Tests

1. Run PHPCS unit tests on the custom sniff:
   ./vendor/bin/phpunit phpcs-sniffs/PluginCheck/Tests/CodeAnalysis/RuntimeFatalErrorPreventionUnitTest.php

Result: Works as expected (All tests pass)

Test 2: Run Plugin Check PHPUnit Integration Tests

1. Start the test stack: npm run wp-env:start:tests
2. Run checker unit tests:
   npm run test-php -- --filter=Runtime_Fatal_Error_Prevention_Check_Tests

Result: Works as expected (All tests pass)

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Co-authored-by: faisalahammad <faisalahammad@git.wordpress.org>
Co-authored-by: davidperezgar <davidperez@git.wordpress.org>

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