Performance improvements

[const-cloudinary]

Memoize hot lookups and tighten array helpers used during transformation URL building:

• StringUtils: cache snakeCaseToCamelCase / camelCaseToSnakeCase results keyed by input (and separator when non-default). Inputs are bounded by SDK property/config names, so the caches saturate immediately.
• ClassUtils: cache the unfiltered ReflectionClass::getConstants() result per class name. Exclusions are applied after the cache lookup so the cache is not polluted by per-call filters.
• ArrayUtils: replace array_values()-based isAssoc with array_is_list(); add fast paths in safeFilterFunc for null and string; refactor safeImplode into a single foreach that only touches float values.

These changes complement the cloudinary_php Configuration clone fast-path and together drop URL build cost from ~361 µs/op to ~28 µs/op on the profiling workload, with no measurable memory growth (caches saturate at ~7 KB total and never grow with workload).

Brief Summary of Changes

What does this PR address?

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

Are tests included?

• Yes
• No

Reviewer, please note:

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.