[FEATURE] Cypress testing rule edit enhancement

[djindjic]

Is your feature request related to a problem?
Reuse <EuiCodeEditor> content expects base on this PR comment.
#201 (comment)

[djindjic]

As pointed out in PR comment referenced in issues description, I've reused same selector [class="euiCodeBlock__line"] to iterate through <EuiCodeBlock> on rule details flyout YAML content. Unfortunately, this is not possible to do in similar way on <EuiCodeEditor> on rule edit mode, but it's still covered by already existing contains like expectations.

Keeping @AWSHurneyt in the line based on our offline discussion. If we are able to give a feedback to OIU team, we could also propose additional data-test-subj attributes on either <EuiCodeBlock> and <EuiCodeEditor> to avoid targeting inner elements on class attribute.