Mosquitto in Codebuild CI

[TwistedTwigleg]

Description of changes:

Adds installing and running Mosquitto in Codebuild CI. This makes our Codebuild CI more standalone and ensures we can always run the basic MQTT5 tests.

• Doing this required modifying the HTTP proxy tests to run against IoT Core.
  • Adds a shell script to install Mosquttio (and dependencies) in Codebuild. Building from source to use version new enough to work for our purposes (apt-get uses too old of a version for what we need).
• Unfortunately this adds about 6-10 minutes of extra time to the Codebuild Job.

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

[TwistedTwigleg]

As discussed: Getting Mosquitto in Codebuild CI is not planned at this time. Closing...