refactor(@angular/build): prevent key collisions in cache namespaces

[clydin]

Previously, Cache formatted keys by joining the namespace and key with a single colon delimiter (${namespace}:${key}). This allowed potential key collisions if a namespace contained colons (such as 'a' with key 'b:c' versus 'a:b' with key 'c').

While this was not an issue in existing usages because all current namespaces are fixed, colon-free identifiers and keys are hash digests, it presented an architectural risk as caching usages expand.

Namespacing is now encapsulated in a dedicated NamespacedCacheStore wrapper that frames keys using length-prefix encoding (<length>:<namespace>:<key>). The length prefix eliminates delimiter ambiguity regardless of what characters appear in the namespace or key. Additionally, Cache has been decoupled from namespace management, simplifying MemoryCache and internal request tracking.

[gemini-code-assist]

Code Review

This pull request introduces a new NamespacedCacheStore class to handle key namespacing using length-prefix framing, which prevents key collisions. It refactors the Cache class to delegate namespacing to this wrapper and updates both LmdbCacheStore and SqliteCacheStore to use it. The feedback suggests decoupling NamespacedCacheStore from the specific value type of the underlying store by using CacheStore<any>, and explicitly specifying the type argument <V> when instantiating Cache and NamespacedCacheStore in the cache stores to ensure strict type safety.