Deduplicate PHP version branching in RectorConfigBuilder

[TomasVotruba]

Follow-up to #8225, same class, same kind of copy-paste.

withPhpSets()

16 bool flags were dispatched through nine early-return blocks followed by a seven-arm elseif chain:

if ($php53) {
    $this->withPhp53Sets();
    return $this;
}

// ... php54, php55, php56, php70, php71, php72, php73, php74 ...

if ($php80) {
    $targetPhpVersion = PhpVersion::PHP_80;
} elseif ($php81) {
    $targetPhpVersion = PhpVersion::PHP_81;
} elseif ($php82) {
// ... through php86 ...
} else {
    throw new InvalidConfigurationException('Invalid PHP version set');
}

Now one version-keyed table:

$pickedPhpVersions = array_keys(array_filter([
    PhpVersion::PHP_53 => $php53,
    // ...
    PhpVersion::PHP_86 => $php86,
]));

which also drops the func_get_args() indirection previously needed to count how many flags were set. The unreachable 'Invalid PHP version set' branch goes with it — by that point a non-empty pick list always has exactly one entry.

withDowngradeSets()

Same shape, nine arms:

-if ($php84) {
-    $this->sets[] = DowngradeLevelSetList::DOWN_TO_PHP_84;
-} elseif ($php83) {
-    $this->sets[] = DowngradeLevelSetList::DOWN_TO_PHP_83;
-} elseif ($php82) {
-// ... through php71 ...
-}
+$pickedDowngradeSets = array_keys(array_filter([
+    DowngradeLevelSetList::DOWN_TO_PHP_84 => $php84,
+    // ...
+    DowngradeLevelSetList::DOWN_TO_PHP_71 => $php71,
+]));

The nine withPhpNNSets() methods

Each had the same three-line body:

public function withPhp70Sets(): self
{
    $this->isWithPhpSetsUsed = true;

    $this->sets = array_merge($this->sets, PhpLevelSetResolver::resolveFromPhpVersion(PhpVersion::PHP_70));

    return $this;
}

becomes

public function withPhp70Sets(): self
{
    return $this->addPhpLevelSets(PhpVersion::PHP_70);
}

withPhpSets() reuses the same private helper for both the picked-version and the composer.json-resolved path.

Behavior

Public API unchanged, and unlike #8225 no message or exception type changes here.

These paths have no direct test coverage, so I checked parity by driving the builder through 14 cases and reading back the resolved set list by reflection on both old and new code: no args, each of php53/php74/php80/php86, explicit php80: false, the withPhpNNSets() equivalents, both downgrade targets, and the four throwing cases (two versions picked, withPhpSets() called twice, no downgrade target, two downgrade targets). Output identical across all 14.

Net -83 lines.