feat: Slight performance improvements

[kissifrot]

Brief Summary of Changes

Several targeted performance improvements on the serialization hot path (qualifier key/name resolution, multi-value qualifier rendering), plus a regression test and expanded coverage for isJsonString().
No external behavior change.

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What does this PR address?

• GitHub issue (Add reference - #XX)
• Refactoring
• New feature
• Bug fix
• Adds more tests

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Are tests included?

• Yes
• No

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Details

• QualifierMultiValue::__toString() — mutation bug fix (biggest gain) EffectName argument keys were appended directly to $this->argumentOrder on every call. Any code path serializing the same qualifier more than once (URL generation loops, logging, test assertions) caused $argumentOrder to grow unboundedly, degrading sort performance on subsequent calls.
  Fix: operate on a local copy of $argumentOrder inside __toString().

• BaseQualifier::getKey() — per-class static cache
  getKey() invoked getName() + StringUtils::toAcronym() on every call.
  The result depends solely on the class name and is immutable per process.
  Added a private static array $keyCache keyed by static::class (Late Static Binding) so each concrete subclass pays the derivation cost once.

• BaseComponent::getName() — per-class static cache
  Same rationale: getName() called ClassUtils::getBaseName() + StringUtils::camelCaseToSnakeCase() on every invocation. Added private static array $nameCache with the same LSB pattern.

• JsonUtils::isJsonString() — fast path + PHP 8.3+

  • Added a first-character guard ({ or [) before any parsing, preserving the original semantics of accepting only JSON objects and arrays.
  • PHP 8.3+: delegates to json_validate(), which validates JSON syntax without building a decoded value in memory.

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Benchmark

Scenario	Before	After	Gain
Qualifier serialized ×10 (mutation fix)	7 092 ms	395 ms	×18
Full pipeline — single step	527 ms	243 ms	×2.2
Full pipeline — multi step	1 339 ms	689 ms	×1.9
Full pipeline — complex (overlay)	2 468 ms	1 707 ms	×1.4
isJsonString() — large payload	84 ms	68 ms	×1.2

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Reviewer, please note:

• The $nameCache / $keyCache arrays live on the respective base classes and are keyed by static::class, so each concrete subclass gets its own entry while the storage stays on the base class. The caches are per-process (transparently reset on each PHP-FPM request).
• The QualifierMultiValue change is a pure bug fix — the old code produced incorrect sort order after the first __toString() call on any instance whose EffectName arguments were not pre-sorted. A regression test is included in EffectTest::testEffectQualifierToStringIsIdempotent().
• isJsonString() behaviour is unchanged with one narrow exception: strings with leading whitespace before {/[ (e.g. " {}") now return false.
  This was not a supported use-case in practice (configs are always programmatically generated without leading whitespace), but indicate me if I need to alter it 👍

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Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I ran the full test suite before pushing the changes and all the tests pass.

[kissifrot]

@const-cloudinary if you happen to pass by 😇 🙏