Skip non-template keys when a constant offset misses ConstantArrayType's key index

[Kocal]

In ConstantArrayType::recursiveHasOffsetValueType(), a constant offset (ConstantStringType / ConstantIntegerType) whose value isn't in the key index used to fall through to a scan calling isSuperTypeOf() on every key of the array. A non-template constant key can only answer "no" there, since its isSuperTypeOf() compares values of the same class, so those keys are now skipped. Template keys are still compared, and the unsealed-extras handling after the scan is unchanged. The turbo-ext mirror (ConstantArrayType.cpp) gets the same change.

This matters when a literal array is passed to a parameter typed with a large shape, like the symfony/ux-css CssStyles shape (847 keys): checkOurKeys() asks the literal array's hasOffsetValueType() for every key of the shape, and each miss used to compare against every key of the literal array.

As a safety check, I temporarily logged the result of every skipped comparison over the full test suite and PHPStan's self-analysis: 5.6M skipped comparisons, all of them "no".

The baseline grows by one more instanceof ConstantStringType in ConstantArrayType.php (5 -> 6), on purpose: the skip relies on the exact class, since only then does isSuperTypeOf() compare values.

Benchmarked with 50 calls to CssRuntime::css() using literal arrays against the nested shape from the reproducer, --debug, interleaved runs:

Build	Before	After
On top of #6652, #6671, #6672, #6673 + #6675 (no turbo)	1.56-1.59 s	1.43-1.49 s
Plain 2.3.x (no turbo)	1 min 12 s	1 min 12 s
Plain 2.3.x (turbo)	22.11-22.68 s	22.07-22.55 s
PHPStan analysing its own src/Type	28.13-28.29 s	28.08-28.71 s

The gain only shows up on top of the other PRs: elsewhere the walks they remove dominate.

make tests passes with and without the extension, make phpstan and make cs pass, turbo's smoke.php, side-by-side.php and signature-parity.php pass, and --error-format=raw output is byte-identical with the extension on and off.

Refs phpstan/phpstan#15348