Add a --debug (-d) flag to ddev env test

[alopezz]

What does this PR do?

Adds a new --debug option that gets passed to the test command and has the same behaviour as that for ddev test.

Motivation

I wanted to be able to see output from prints while running tests.

Additional Notes

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• PR title must be written as a CHANGELOG entry (see why)
• Files changes must correspond to the primary purpose of the PR as described in the title (small unrelated changes should have their own PR)
• PR must have changelog/ and integration/ labels attached

[codecov]

Codecov Report

Merging #12379 (230a6bb) into master (de95835) will increase coverage by 0.00%.
The diff coverage is n/a.

Flag	Coverage Δ
arangodb	98.21% <ø> (ø)
azure_iot_edge	82.00% <ø> (ø)
cacti	83.95% <ø> (ø)
calico	83.33% <ø> (ø)
ecs_fargate	80.23% <ø> (ø)
hazelcast	92.39% <ø> (ø)
istio	77.65% <ø> (+0.55%)	⬆️
linkerd	85.14% <ø> (+1.14%)	⬆️

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