Final request-response polish

[bretambrose]

Full MQTT request-response client and subsystem implementation

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 68.88889% with 14 lines in your changes missing coverage. Please review.

Project coverage is 84.04%. Comparing base (cbb958e) to head (08ef51d).

Files with missing lines	Patch %	Lines
source/request-response/protocol_adapter.c	0.00%	6 Missing ⚠️
source/request-response/request_response_client.c	81.25%	3 Missing ⚠️
source/request-response/subscription_manager.c	0.00%	2 Missing ⚠️
source/client_channel_handler.c	66.66%	1 Missing ⚠️
source/v5/mqtt5_client.c	91.66%	1 Missing ⚠️
source/v5/mqtt5_topic_alias.c	0.00%	1 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##           Elastishadow     #367   +/-   ##
=============================================
  Coverage         84.03%   84.04%           
=============================================
  Files                24       24           
  Lines             10331    10343   +12     
=============================================
+ Hits               8682     8693   +11     
- Misses             1649     1650    +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.