Investigate cheaper no-interning and multi-isolate cache sharing for NormalizedPath

[coderabbitai]

Background

PR #343 makes the NormalizedPath interning cache configurable (via the new Cache<K, V> interface, LruCache, and NoCache implementations). While this addresses the performance cliff identified in #342 and #118, a follow-up investigation is needed.

Problem

• The current approach (even with NoCache) may not be as cheap as possible when interning is disabled. There may be room to make the no-interning path even lighter.
• Dart-side caches (including LruCache) cannot be shared across isolates. This significantly limits their effectiveness in multi-isolate deployments, where each isolate maintains its own separate cache with no shared benefit.

Tasks

• Investigate whether the no-interning (NoCache) code path can be made even cheaper (e.g., avoiding unnecessary allocations or lookups entirely).
• Investigate options for cache sharing or coordination across isolates (e.g., using SendPort/ReceivePort, native code, or alternative architectural approaches).
• Document the multi-isolate limitation clearly in the public API if no sharing solution is feasible.

References

• PR: feat: Make NormalizedPath interning cache configurable #343
• Comment: feat: Make NormalizedPath interning cache configurable #343 (comment) pr view 343 --repo serverpod/relic --json comments --jq '.comments[-1].id' 2>/dev/null || echo 'see-pr-343')
• Fixes Performance cliff on high-cardinality dynamic paths due to NormalizedPath interning #342, Improve interning of NormalizedPath #118

Requested by

@nielsenko