Enable FileCacheStorage for OptimizedDirectorySourceLocatorFactory in tests

[staabm]

the caching in

phpstan-src/src/Reflection/BetterReflection/SourceLocator/OptimizedDirectorySourceLocatorFactory.php

Lines 57 to 76 in 1a8a657

	/** @var array<string, array{string, string[], string[], string[]}>|null $cached */
	$cached = $this->cache->load($cacheKey, $variableCacheKey);
	if ($cached !== null) {
	foreach ($cached as $file => [$hash, $classes, $functions, $constants]) {
	if (!array_key_exists($file, $fileHashes)) {
	unset($cached[$file]);
	continue;
	}
	$newHash = $fileHashes[$file];
	unset($fileHashes[$file]);
	if ($hash === $newHash) {
	continue;
	}
	[$newClasses, $newFunctions, $newConstants] = $this->findSymbols($file);
	$cached[$file] = [$newHash, $newClasses, $newFunctions, $newConstants];
	}
	} else {
	$cached = [];
	}

re-valides the cache contents via sha1_file() hashes. I think we can utilize this cache also for our test-suite.

---

running php tests/vendor/bin/paratest..

before this PR:

Time: 00:46.365, Memory: 636.50 MB

OK, but some tests were skipped!
Tests: 13381, Assertions: 80652, Skipped: 170.

after this PR:

...
Time: 00:41.428, Memory: 618.50 MB

OK, but some tests were skipped!
Tests: 13381, Assertions: 80652, Skipped: 170.

---

this will NOT solve phpstan/phpstan#13852 as it only affects the test-suite

[ondrejmirtes]

Thank you!