[throttler-storage-redis] Improvement: consider SCRIPT LOAD with EVALSHA

[bplies-ATX]

The Redis script body could be improved by storing it Redis-side with SCRIPT LOAD (docs) so that it can be defined once and reused rather than re-submitted on each request. That should save a lot of network bytes over time as well as any script re-parsing.

Valkey has a nice writeup about this.

Whenever we call EVAL, we also include the script's source code with the request. Repeatedly calling EVAL to execute the same set of parameterized scripts, wastes both network bandwidth and also has some overheads in Valkey. Naturally, saving on network and compute resources is key, so, instead, Valkey provides a caching mechanism for scripts.