feat: ai rate limiting redis support

[beardnick]

Description

Which issue(s) this PR fixes:

Fixes #12482

Notice

• I have updated the limit-count-redis.lua and limit-count-redis-cluster.lua files to ensure they now support rate-limiting during the log phase.
• I referred to the limit-conn-redis.lua file as a guide while implementing rate-limiting in the log phase.
• To ensure a clean testing environment, I added the require("lib.test_redis").flush_all() function to every Redis rate-limiting test case. Without this addition, the tests could fail unpredictably.
• I have adjusted the expected results in limit-req-redis.t and limit-req-redis-cluster.t test cases. After thorough verification, the correct behavior is [200, 403, 403, 403]. Previously, the results appeared as [403, 403, 403, 403] due to Redis not being properly cleaned beforehand.

Checklist

• I have explained the need for this PR and the problem it solves
• I have explained the changes or the new features added to this PR
• I have added tests corresponding to this change
• I have updated the documentation to reflect this change
• I have verified that this change is backward compatible (If not, please discuss on the APISIX mailing list first)

[beardnick]

@Baoyuantop PTAL

[membphis]

@beardnick many thx for your contribution, some CI tests are failed, you can fix them

[nic-6443]

This code should be placed in the ai-rate-limiting plugin, not in the limit-count plugin itself, because this code is only useful for ai-rate-limiting.

[beardnick]

I disagree. Similar logic also appears in the limit-conn.

apisix/apisix/plugins/limit-conn/limit-conn-redis.lua

Lines 60 to 81 in 7e907a5

	local function leaving_thread(premature, self, key, req_latency)
	local conf = self.conf
	local red, err = redis.new(conf)
	if not red then
	return red, err
	end
	return util.leaving(self, red, key, req_latency)
	end
	function _M.leaving(self, key, req_latency)
	-- log_by_lua can't use cosocket
	local ok, err = ngx_timer_at(0, leaving_thread, self, key, req_latency)
	if not ok then
	core.log.error("failed to create timer: ", err)
	return nil, err
	end
	return ok
	end

If I put this logic into ai-rate-limiting plugin, it will make the plugin too complicated. I have to copy a lot of logic from limit-count. Currently, the ai-rate-limiting is just a simple wrapper of limit-count.

Or, do you think I need to rewrite the ai-rate-limiting to something like limit-ai-redis.lua and limit-ai-redis-cluster.lua?

[beardnick]

This PR is quite large and hard to review. If you agree, I can split it into 3 separate PRs:

1. A PR to improve the tests for the rate-limiting plugins.
2. A PR to add support for the log phase.
3. A PR to add Redis support to the ai-rate-limiting.

[nic-6443]

Look like the changes in this PR should be limited to the ai-rate-limiting plugin and minor tweaks to the limit-count plugin. The current PR modifies too much code and test cases for other rate limiting plugins, expanding its scope. We should minimize unnecessary code changes.

[AlinsRan]

It is recommended to use multi worker testing for Redis related tasks in the new test file.