feat(sdk): make SDK caches configurable with audit logging and central flush

[eugenioenko]

Motivation

Both kasKeyCache and kasAllowlistCache use hardcoded 5-minute TTLs with no configurability, no central flush mechanism, and no audit logging for cache hits/misses. Customer environments need the ability to configure, manage, and flush these caches.

Raised in #3898 by @jrschumacher.

Requirements

• Configurable TTL for kasKeyCache and kasAllowlistCache
• Central way to flush/invalidate caches
• Audit logging for cache hits and misses
• Consistent behavior across both caches

Related: #3899 (mutex/concurrency safety for both caches)

Notes

https://github.com/opentdf/web-sdk/ and https://github.com/opentdf/java-sdk/ both have the same issues with cache.
In case of WebSDK, Key Cache doesn't even have a TTL