Replace PrefixPool with netaddr.IPSet

[PhillSimonds]

Fixes #3547

[codspeed-hq]

CodSpeed Performance Report

Merging #4896 will improve performances by 21.14%

_{Comparing PhillSimonds:ps-issue-3547 (2596f90) with develop (485838f)}

Summary

⚡ 1 improvements
✅ 9 untouched benchmarks

Benchmarks breakdown

	Benchmark	develop	PhillSimonds:ps-issue-3547	Change
⚡	test_schemabranch_duplicate	377.9 µs	312 µs	+21.14%

[gmazoyer]

Seeing the tests still failing, I wonder if switching to IPSet actually fixes some bug we did not know about. I'll have a deeper look.

[gmazoyer]

Seeing the tests still failing, I wonder if switching to IPSet actually fixes some bug we did not know about. I'll have a deeper look.

Having gone through the changes, I believe the test failures actually highlight wrong expected results in the first place. We should therefore fix these wrong expected results.