Refactor response writes, test refactors, fix UNPACK_TCP_STATE_FROM_TCP_INFO location

[MSP-Greg]

Description

1. request.rb
   1.1. Refactor handle_request
   1.2. Refactor and simplify fast_write for fewer string assignments

2. minissl.rb
   2.1. Refactor and simplify write for fewer string assignments

3. server.rb
   3.1 Move UNPACK_TCP_STATE_FROM_TCP_INFO to correct location
   3.2. Add PURGE_INTERRUPT_QUEUE constant
   3.3. Refactor cork_socket, uncork_socket, & closed_socket? to work with ssl sockets
   3.4. Return from above before entering begin block
   3.5 Anchor Ruby 'root' constants, e.g. Socket and TCPSocket

4. test_puma_server.rb
   4.1 Add multi-byte characters to test_very_large_return
   4.2 Cleanup @server.stop code, misc

5. test_puma_server_ssl.rb
   5.1. Add multi-byte characters to test_very_large_return
   5.2. Rename a few variables, quotes, misc

NOTES:

Code refactors done while working on updated test framework.

CI using updated tests - MRI, non-MRI. At the bottom of the test step log, see 'Debugging Info`, and click open to see various integration test info.

Closes #2556

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[MSP-Greg]

Also added a fix for check_changelog.yml, missing a paren...

REMOVED: see b0bd212

[dentarg]

Also added a fix for check_changelog.yml, missing a paren...

Oops, my bad (26776c8), however, I think you could add that paren directly to master :)

[MSP-Greg]

Rebased

[MSP-Greg]

Closing in favor of #2595. I will extract test updates and maybe a few lib updates (3.3, 3.4, ??) from this into another pr...