fix(liveness): LivenessCoordinator uses a coroutine scope that cancels on destroy

[mattcreaser]

• PR conforms to Pull Request guidelines.

Issue #, if available:

Description of changes:
Liveness launches a series of coroutines from the LivenessCoordinator. These were not bound to a controlled coroutine scope, causing the coroutines to potentially outlive the desired lifetime of the Coordinator instance. In particular, the 5 second delay in launchCamera could cause a session error after the LivenessCoordinator was already destroyed.

Updated to hold on to the coroutine scope and cancel when the instance is destroyed.

How did you test these changes?

• Verified that the timeout is cancelled if the coordinator is destroyed.
• Verified that resources are cleaned up after the coordinator is destroyed.

Documentation update required?

• No
• Yes (Please include a PR link for the documentation update)

General Checklist

• Added Unit Tests
• Added Integration Tests
• Security oriented best practices and standards are followed (e.g. using input sanitization, principle of least privilege, etc)
• Ensure commit message has the appropriate scope (e.g fix(liveness): message, fix(authenticator): message, fix(all): message)

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

[codecov]

Codecov Report

❌ Patch coverage is 0% with 23 lines in your changes missing coverage. Please review.
✅ Project coverage is 32.61%. Comparing base (5168db7) to head (5c8695a).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #275      +/-   ##
==========================================
- Coverage   32.65%   32.61%   -0.05%     
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  Files         100      100              
  Lines        4621     4627       +6     
  Branches      587      589       +2     
==========================================
  Hits         1509     1509              
- Misses       2956     2962       +6     
  Partials      156      156              

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