test(control-plane): separate orchestration tests from EC2 provider tests #5236

Problem

PR #5234 moves the EC2 implementation into the shared runner-provider package. Two EC2 test files still contain a mixture of generic control-plane orchestration tests and EC2-specific provider tests:

• lambdas/libs/runner-providers/aws/ec2/src/control-plane/scale-up.test.ts
• lambdas/libs/runner-providers/aws/ec2/src/control-plane/scale-down.test.ts

To preserve the existing coverage without making that refactor harder to review, these files temporarily import control-plane modules through ../../../../../../functions/control-plane.

The tests cannot be moved as complete files: individual orchestration cases need to move to the control-plane package while EC2 implementation cases remain beside the provider.

Scope

• Identify tests that exercise generic control-plane scale-up and scale-down orchestration.
• Move those cases to lambdas/functions/control-plane and test them through provider interfaces or the existing provider contracts.
• Keep EC2-specific behavior, including EC2 resource operations and dynamic configuration, under lambdas/libs/runner-providers/aws/ec2.
• Remove direct imports and mocks from the EC2 provider tests into functions/control-plane.
• Preserve the existing behavioral coverage while separating ownership clearly.

Acceptance criteria

• No test under lambdas/libs/runner-providers imports from lambdas/functions/control-plane.
• Generic orchestration tests are owned by the control-plane package.
• EC2 implementation tests remain owned by the EC2 provider package.
• Runner-provider and control-plane test suites pass.
• Coverage scopes and thresholds remain valid after the tests are separated.
• Production behavior is unchanged.

Related work

• Follow-up to refactor(runners): introduce provider plugin framework #5234.