perf: optimize batch policy removal

[huynhanx03]

Overview

Optimize batch policy removal by rebuilding Policy and PolicyMap once in RemovePoliciesWithAffected. The previous implementation removed each rule one by one and updated policy indexes after every deletion, which becomes expensive for large batch removals.

Change

• Remove policies in batch by collecting keys, compacting Policy, and rebuilding PolicyMap once.
• Add BenchmarkRemovePoliciesLarge to cover batch removal performance.

Benchmark

goos:  darwin
goarch: arm64
cpu:   Apple M1

BenchmarkRemovePoliciesLarge
metric      old       new      delta
ns/op       481,529   14,657   -97.0%
B/op        155,938   12,660   -91.9%
allocs/op   5,159     207      -96.0%