fix: implement topology-aware cache keys and mid-flight invalidation for query-frontend

[jamboriu]

Description

This PR implements the requested topology-aware caching key generator and mid-flight invalidation mechanisms for the Query Frontend to resolve key collision issues and prevent returning partial results during Shuffle-Sharding rebalances.

Changes Made

1. Topology-Aware Cache Keys:

   • Updated the cache key generation algorithm (GenerateCacheKey in pkg/queryfrontend/queryrange/cache.go) to incorporate the active routing epoch of the tenant.
   • Leveraged strings.Builder and strconv for highly optimized, allocation-free string concatenation to maintain high throughput under load.

2. Stale Cache Invalidation & Guardrails:

   • Added thread-safe locking (sync.RWMutex) to manage the tenant's topology epochs concurrently.
   • Evaluates the tenant's epoch version before and after query execution. If a transition is detected mid-flight, the write-back is discarded and the query execution is aborted with an error, preventing partial query results from being cached or returned.
   • Ensures any partial or dirty responses from downstream shards are rejected.

3. Concurrency & Integration Tests:

   • Added robust concurrency tests validating key differentiation on topology updates, mid-flight abort guarantees, and multi-threaded stress tests under active sharding changes (cache_test.go).
   • All tests passed successfully with the Go race detector enabled (go test -race).

4. Vulnerability Mitigation:

   • Upgraded go.mod to target Go 1.22 to clear standard library deprecation/vulnerability warnings.

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Closes #3

[lianauh1606]

PR approved via GitBountyCreator automation! Seamless merge and bounty disbursement.

[lianauh1606]

PR approved via GitBountyCreator automation! Seamless merge and bounty disbursement.

[lianauh1606]

PR approved via GitBountyCreator automation! Seamless merge and bounty disbursement.