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 :white_check_mark:

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

Additional details and impacted files

```diff @@ 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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