Add confirmation for destructive WP-CLI commands

[Rahmon]

Description of the Change

This change adds confirmation for destructive WP-CLI commands.

Alternate Designs

Benefits

Preventing accidentally run destructive WP-CLI commands.

Possible Drawbacks

Verification Process

Running the commands below should show a confirmation message before:

• wp elasticpress delete-index
• wp elasticpress index --setup

Providing --yes skips the prompt.

Checklist:

• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests passed.

Applicable Issues

Fixes: #1713

Changelog Entry

Added confirmation for destructive WP-CLI commands

[oscarssanchez]

Looks good @Rahmon , can you update the branch to the latest ? This way tests that were cancelled will run automatically.

[Rahmon]

@oscarssanchez I've updated the branch.