chore(test): eliminate duplicate mig http_server

[StarlightIbuki]

Summary

Some tests are using their own copy of http_server, and some are using static ports for testing. Some also do not kill the thread if the test fails.

Solution: see Full changelog.

Checklist

（Do we need to backport this?)

• The Pull Request has backports to all the versions it needs to cover

Full changelog

• Rewrite to use the http_server in the helper;
• Rewrite to use dynamic ports for every test;
• Kill threads at after_each

Issue reference

Partial fix of KAG-1148

[StarlightIbuki]

Closing as we have a new HTTP mocking implementation.
Refer: #10885