[lambda] Fix interactive API key validation

[swfunc]

What and why?

We noticed that the interactive CLI was using the plaintext API validation rules incorrectly when customers had chosen either the KMS encrypted key or the Secrets Manager key ARN. This PR fixes the validation to accommodate for the different formats of API key.

How?

Fixes the validation function for the text prompt input

Review checklist

• [x] Feature or bugfix MUST have appropriate tests (unit, integration)
• [ ] [Synthetics] New releases of datadog-ci MUST be followed by a synthetics-ci-github-action release
• [ ] [Synthetics] New releases of datadog-ci MUST be followed by a datadog-ci-azure-devops release

[datadog-datadog-prod-us1[bot]]

Datadog Report

Branch report: stephenf/fix-interactive-api-key-validation Commit report: 5026a3d

:white_check_mark: datadog-ci-tests 0 Failed, 0 New Flaky, 1167 Passed, 0 Skipped, 50.85s Wall Time

[datadog-datadog-prod-us1[bot]]

Datadog Report

Branch report: stephenf/fix-interactive-api-key-validation Commit report: 9630267

:white_check_mark: datadog-ci-tests 0 Failed, 0 New Flaky, 3672 Passed, 0 Skipped, 1m 13.2s Wall Time