Refactor MQTT5 ping timeout

[bretambrose]

• Relaxes validation on ping timeout configuration value.
• Ping timeout now a function of base configuration value and the connection's negotiated keep alive.

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

All modified and coverable lines are covered by tests ✅

Project coverage is 82.61%. Comparing base (74da9ca) to head (20ab43b).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #361      +/-   ##
==========================================
+ Coverage   82.60%   82.61%   +0.01%     
==========================================
  Files          20       20              
  Lines        8767     8756      -11     
==========================================
- Hits         7242     7234       -8     
+ Misses       1525     1522       -3     

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[sbSteveK]

Trivial: Should this log only occur when the set ping timout is dynamically altered? i.e. in the if block that checks whether we should apply the half_keep_alive_nanos ?

[bretambrose]

I think it's fine the way it is as a direct reminder so that you don't have to have access to the log of the original settings to know.

Trivial: Should this log only occur when the set ping timout is dynamically altered? i.e. in the if block that checks whether we should apply the half_keep_alive_nanos ?