Investigate parallelizing CI testing jobs

Investigate parallelizing CI testing jobs - for example, if unit tests for Core, Lifecycle, Identity, etc run in sequential order, see how they can be parallelized to save time. Especially relevant if the current CircleCI CI script is converted to a reusable GitHub Actions workflow

### Expected Behaviour

### Actual Behaviour

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#### Steps to Reproduce

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#### Sample Code that illustrates the problem

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Start by locating the current CircleCI configuration and mapping the Core, Lifecycle, Identity, and other test jobs and their dependencies. Compare that setup with a reusable GitHub Actions workflow, then verify that independent jobs run in parallel, all tests still pass, and CI time is reduced.

Written by the indexing model from the issue text.