feat(integ-runner): add --strict flag to throw error on missing tests

[abidhasan-aws]

Description of the change

This PR adds a new flag --strict to integ-runner. When enabled, this flag enforces that all specified tests are found and can be run.

With strict = true, integ-runner will throw an error when any specified tests are not found.

Reason for this change

For the Integration Test Workflow, we want to throw an error if some specified tests are not found. This ensures that all tests that have been changed in a PR are actually run in the workflow.

Currently, integ-runner does not throw an error when tests are not found. We can use the --strict flag in the workflow for our use case.

Test

Added unit tests to verify the functionality of the new flag.

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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.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.02%. Comparing base (d1b4113) to head (a1b2938).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #929      +/-   ##
==========================================
- Coverage   83.45%   83.02%   -0.44%     
==========================================
  Files          71       71              
  Lines       10401    10401              
  Branches     1317     1303      -14     
==========================================
- Hits         8680     8635      -45     
- Misses       1680     1727      +47     
+ Partials       41       39       -2     

Flag	Coverage Δ
suite.unit	83.02% <ø> (-0.44%)	⬇️

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[mrgrain]

LGTM