[feature] add jq filter cache

[ldmonster]

Overview

Cache compiled JQ filters: parse and compile each jqFilter expression once at hook-config load time instead of on every Kubernetes event.

What this PR does / why we need it

Every Kubernetes event that reaches a hook with a jqFilter previously triggered a full gojq.Parse + implicit compilation cycle before running the expression against the object. For hooks watching high-churn resources (Pods, Events, custom CRDs with many replicas) this is a measurable, unnecessary CPU cost that accumulates proportionally to event rate × number of monitored bindings.

This PR:

• Introduces CompiledFilter interface in filter.go — a pre-compiled filter with a single Apply(data) ([]byte, error) method.
• Adds CompiledJqFilter struct in apply.go backed by *gojq.Code (the compiled representation returned by gojq.Compile). A Compile(string) constructor parses and compiles the expression once. A shared collectResults helper is extracted so both the interpreted (Filter.ApplyFilter) and compiled (CompiledJqFilter.Apply) paths stay DRY.
• Adds CompiledJqFilter filter.CompiledFilter field to MonitorConfig and a WithJqFilter(string) error method that atomically sets the raw string (kept for metadata/logging) and compiles it. Config parse errors for invalid jqFilter expressions are caught immediately at startup, not at first event.
• Updates config parsing in config_v0.go and config_v1.go to call monitor.WithJqFilter(...) instead of plain field assignment — invalid expressions are now rejected at hook-config load time with a descriptive error.
• In resource_informer.go, removes the two per-event jq.NewFilter() allocations and passes ei.Monitor.CompiledJqFilter directly to applyFilter. The jqFilter string is still forwarded as a separate argument purely for res.Metadata.JqFilter (used by the binding-context JSON marshaler).
• applyFilter signature simplified from (jqFilter string, fl filter.Filter, ...) to (compiledFilter filter.CompiledFilter, jqFilterStr string, ...).

Performance impact:
gojq.Parse + gojq.Compile run once per binding at startup. Per-event cost is reduced to code.Run(data) only.