Build e2e test fixtures with Release configuration

[twometresteve]

Goal

Refactor the e2e test setup to run tests against fixtures built in the Release configuration.

Design

The e2e tests have been run against Debug configuration fixtures for some time for convenience of testing some functionality, but it's more representative overall to run in Release configuration.

This PR refactors the pipeline to run in Release mode and lays the tracks for running in Debug mode, but the actual running of Debug tests will follow in a separate PR.

Changeset

• All existing feature file moved into features/release
• Test scenarios with steps that need Debug configuration are duplicated under features/debug
• Expectations that fail in Release mode (typically due to compile optimisation) are removed from the Release fixture (just the failing steps are removed, the scenarios are still all run).

Some tests are failing on macOS only and I've raised PLAT-12396 to look at those in more depth.

Testing

Covered by a full CI run.

[github-actions[bot]]

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