Adapter subscriptions

[bretambrose]

Shared subscription set implementation

• Topic tree support for mqtt 311 per-subscription publish received callbacks
• Per-topic-filter subscription record tracking for resubscribe support
• The subscription set could eventually replace the topic tree in the mqtt 311 implementation, but for now leave it alone

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

Patch coverage: 97.22% and project coverage change: +0.43 :tada:

Comparison is base (07bfc59) 81.11% compared to head (a09799a) 81.54%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## AdapterOperationalState #302 +/- ## =========================================================== + Coverage 81.11% 81.54% +0.43% =========================================================== Files 18 19 +1 Lines 7959 8134 +175 =========================================================== + Hits 6456 6633 +177 + Misses 1503 1501 -2 ``` | [Impacted Files](https://app.codecov.io/gh/awslabs/aws-c-mqtt/pull/302?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=awslabs) | Coverage Δ | | |---|---|---| | [source/v5/mqtt5\_topic\_alias.c](https://app.codecov.io/gh/awslabs/aws-c-mqtt/pull/302?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=awslabs#diff-c291cmNlL3Y1L21xdHQ1X3RvcGljX2FsaWFzLmM=) | `96.09% <ø> (-0.08%)` | :arrow_down: | | [source/mqtt\_subscription\_set.c](https://app.codecov.io/gh/awslabs/aws-c-mqtt/pull/302?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=awslabs#diff-c291cmNlL21xdHRfc3Vic2NyaXB0aW9uX3NldC5j) | `97.15% <97.15%> (ø)` | | | [source/client\_impl\_shared.c](https://app.codecov.io/gh/awslabs/aws-c-mqtt/pull/302?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=awslabs#diff-c291cmNlL2NsaWVudF9pbXBsX3NoYXJlZC5j) | `84.61% <100.00%> (+1.28%)` | :arrow_up: | ... and [3 files with indirect coverage changes](https://app.codecov.io/gh/awslabs/aws-c-mqtt/pull/302/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=awslabs)

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