feat(CuckooFilter): add cf.exists and cf.mexists command

[nagisa-kunhah]

task id: #3359

[nagisa-kunhah]

@jihuayu Sorry for the noise. The initial version of this PR branch accidentally contained replayed upstream commits because it was not cleanly rebased onto the latest upstream/unstable. This caused GitHub to show unrelated files in the PR diff and also created automatic cross-references to other PRs from the replayed commit messages.
Can we clear these messages？

[jihuayu]

@nagisa-kunhah Thank you for your contribution. It doesn't matter. I only care about the code diff.
However, please take note: you need to understand all the code you submit, as you will be held ultimately responsible for it.

Please @ me if you have any other questions.

Tips:

• Please read Guidelines for AI-assisted Contributions
• If you used AI tools, please let us know which tools and models you used; this helps us assess the reliability of the code.

[Copilot]

Pull request overview

This PR adds RedisBloom-compatible existence queries for Kvrocks’ CuckooFilter implementation by introducing CF.EXISTS and CF.MEXISTS commands, backed by new read-path APIs in the Cuckoo filter type layer and validated through both Go integration/unit tests and C++ unit tests.

Changes:

• Add CF.EXISTS and CF.MEXISTS command implementations and register them as read-only commands.
• Implement redis::CuckooChain::Exists / MExists using per-sub-filter bucket lookups via a new CuckooSubFilter::Contains helper.
• Add test coverage for missing keys, wrong types, argument validation, ordering, and post-expansion behavior (Go + C++).

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/gocase/unit/type/bloom/cuckoo_filter_test.go	Adds Go tests for cf.exists/cf.mexists, including wrongtype/arity and expansion scenarios.
tests/cppunit/types/cuckoo_filter_test.cc	Adds extensive C++ unit tests for Exists/MExists behavior (including expansion and edge-case items).
src/types/redis_cuckoo_chain.h	Exposes new Exists/MExists APIs on the Cuckoo filter type.
src/types/redis_cuckoo_chain.cc	Implements Exists/MExists by scanning sub-filters and checking bucket slots.
src/types/cuckoo_filter_sub_filter.h	Adds a read-only Contains method for sub-filter membership checks.
src/types/cuckoo_filter_sub_filter.cc	Implements Contains using cached page prefetch + per-slot scans of candidate buckets.
src/storage/redis_metadata.h	Clarifies base_capacity meaning for auto-created vs reserved filters (comment update).
src/commands/cmd_cuckoo_filter.cc	Adds cf.exists and cf.mexists Commander implementations and registers them.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[jihuayu]

Hi @nagisa-kunhah. Thank you for your contribution. Overall, this looks good.

[sonarqubecloud]

Quality Gate failed

Failed conditions
42.0% Coverage on New Code (required ≥ 50%)

See analysis details on SonarQube Cloud

[nagisa-kunhah]

Hi @jihuayu , thank you for your careful review. I have addressed all your comments and added some unit tests. Feel free to @ me if you have any questions.