Compute ConstantArrayType sealed-shape isSuperTypeOf() reasons lazily via IsSuperTypeOfResult closures

[phpstan-bot]

Summary

bug-7581.php (a 33-case switch that builds an array shape key by key inside a foreach
convergence loop) got ~30% slower after the June 2026 "reasons" batch
(57ea87c83, a01080ece, e5caec56f). That batch made ConstantArrayType::isSuperTypeOf()
eagerly build a Sealed array shapes … cannot be intersected explanation — which calls the
expensive describe() on both array shapes — for every sealed-vs-sealed comparison during
union/intersection normalization, even though the reason is almost never rendered. On this
benchmark the reason string was built 22,558 times and displayed 0 times.

This PR keeps the diagnostic but computes it lazily, so the describe() work only happens if
and when the reason is actually turned into an error tip.

Changes

• src/Type/IsSuperTypeOfResult.php: added an optional list<Closure(): string> $lazyReasons
  constructor argument (BC — defaults to []) and a getReasons() accessor that materializes
  and de-duplicates eager + lazy reasons. Every reason-carrying method (and, or,
  decorateReasons, extremeIdentity, maxMin, lazyMaxMin, negate, toAcceptsResult)
  now threads the lazy reasons through unchanged. createNo() gained a matching
  $lazyReasons parameter and keeps returning the shared No singleton only when both reason
  lists are empty.
• src/Type/Constant/ConstantArrayType.php: the two sealed-shape no() branches in
  isSuperTypeOf() now pass sealedArrayShapesCannotBeIntersectedReason() as a
  Closure(): string via createNo(lazyReasons: …) instead of building the string eagerly.
• src/Type/TypeCombinator.php: the two intersect() sites that turn an array intersection
  into a reason-bearing NeverType now read getReasons() so the lazy reason is materialized
  exactly where it is consumed.
• src/Reflection/InitializerExprTypeResolver.php, src/Rules/Comparison/ImpossibleCheckTypeHelper.php,
  src/Rules/Classes/ImpossibleInstanceOfRule.php: switched the reason reads that feed error
  tips from ->reasons to ->getReasons(), so ===/is_*()/instanceof impossibility tips
  keep showing the sealed-shape explanation.
• tests/PHPStan/Type/Constant/ConstantArrayTypeTest.php: new regression test.

Probed and intentionally left as-is:

• The sibling ConstantArrayType::accepts() / AcceptsResult describe-based reasons only run
  on genuine acceptance failures (0 builds on the benchmark), so they are not part of this
  regression.
• The analogous ObjectType::isSuperTypeOf() per-pair reasons were already handled separately
  (0c88c321a, 4be03a5a0).

Root cause

The "reasons" batch attached human-readable explanations directly to the IsSuperTypeOfResult
returned by hot type comparisons. ConstantArrayType's explanation is expensive because it
describe()s both (potentially large) array shapes, and isSuperTypeOf() is called O(n) times
per intersection/union step while the array shape grows, so the cost is roughly quadratic — all
of it discarded because the reason is only shown when a rule renders it. The fix makes the
reason a Closure(): string that runs only when getReasons() is called at a render site.

Test

• Added ConstantArrayTypeTest::testSealedArrayShapesCannotBeIntersectedReasonIsLazy: for two
  disjoint sealed shapes it asserts isSuperTypeOf()->reasons === [] (nothing built eagerly)
  while getReasons() still yields the full Sealed array shapes … cannot be intersected
  message. This fails on the pre-fix code (where ->reasons already contained the eagerly
  built string) and passes after the fix.
• Existing IncompatiblePhpDocTypeRuleTest::testExplainUnresolvable continues to pass,
  proving the tip is still surfaced end-to-end via the NeverType / unresolvable-type path.
• The reason-consuming rule suites (Comparison, ImpossibleInstanceOf,
  ImpossibleCheckType{Function,Method,StaticMethod}Call) and the full Type / Analyser
  suites remain green.

Fixes phpstan/phpstan#14918