Add --skip-restore-prompt to backup-utility for restore process

Add option to skip prompts in backup-utility

Adds new --skip-restore-prompt option for the backup
utility. This sets GITLAB_ASSUME_YES, a feature added in
GitLab 13.4 to skip prompts when the backup script executes.

Improves discoverability of the prompt skip feature for
administrators who script their Gitlab backups.

Changelog: added

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What does this MR do?

Add --skip-restore-prompt to backup-utility for restore process

Connected to: Feature Request - Skip prompts during restore p... (gitlab-org/gitlab#418909 - closed)

Changelog: added

Related issues

Checklist

See Definition of done.

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Required

• Merge Request Title, and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com
• When ready for review, MR is labeled "~workflow::ready for review" per the Distribution MR workflow

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Integration tests added to GitLab QA
• The impact any change in container size has should be evaluated
• New dependencies are managed with dependencies.io