[Doc] fix descriptions, add guide link (backport #54620)

[mergify]

• Add tip "see the overview guide..." to top of the backup, create repository, and restore docs
• Remove unused mdx files
• remove the line ## Description from each file so that the overview page has descriptions for each doc instead of the word Description

What type of PR is this:

• BugFix
• Feature
• Enhancement
• Refactor
• UT
• Doc
• Tool

Does this PR entail a change in behavior?

• Yes, this PR will result in a change in behavior.
• No, this PR will not result in a change in behavior.

If yes, please specify the type of change:

• Interface/UI changes: syntax, type conversion, expression evaluation, display information
• Parameter changes: default values, similar parameters but with different default values
• Policy changes: use new policy to replace old one, functionality automatically enabled
• Feature removed
• Miscellaneous: upgrade & downgrade compatibility, etc.

Checklist:

• I have added test cases for my bug fix or my new feature
• This pr needs user documentation (for new or modified features or behaviors)
  • I have added documentation for my new feature or new function
• This is a backport pr

[mergify]

Cherry-pick of dc79ada has failed:

On branch mergify/bp/branch-3.1/pr-54620
Your branch is up to date with 'origin/branch-3.1'.

You are currently cherry-picking commit dc79ada1d7.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   docs/en/sql-reference/sql-statements/backup_restore/RECOVER.md
	modified:   docs/en/sql-reference/sql-statements/backup_restore/SHOW_REPOSITORIES.md
	modified:   docs/en/sql-reference/sql-statements/backup_restore/SHOW_SNAPSHOT.md
	modified:   docs/zh/sql-reference/sql-statements/backup_restore/RECOVER.md
	modified:   docs/zh/sql-reference/sql-statements/backup_restore/SHOW_REPOSITORIES.md

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	both modified:   docs/en/sql-reference/sql-statements/backup_restore/BACKUP.md
	both modified:   docs/en/sql-reference/sql-statements/backup_restore/CANCEL_BACKUP.md
	both modified:   docs/en/sql-reference/sql-statements/backup_restore/CANCEL_RESTORE.md
	both modified:   docs/en/sql-reference/sql-statements/backup_restore/CREATE_REPOSITORY.md
	both modified:   docs/en/sql-reference/sql-statements/backup_restore/DROP_REPOSITORY.md
	both modified:   docs/en/sql-reference/sql-statements/backup_restore/RESTORE.md
	both modified:   docs/en/sql-reference/sql-statements/backup_restore/SHOW_BACKUP.md
	both modified:   docs/en/sql-reference/sql-statements/backup_restore/SHOW_RESTORE.md
	deleted by them: docs/zh/overview-pages/other-data-types.mdx
	both modified:   docs/zh/sql-reference/sql-statements/backup_restore/BACKUP.md
	both modified:   docs/zh/sql-reference/sql-statements/backup_restore/CANCEL_BACKUP.md
	both modified:   docs/zh/sql-reference/sql-statements/backup_restore/CANCEL_RESTORE.md
	both modified:   docs/zh/sql-reference/sql-statements/backup_restore/CREATE_REPOSITORY.md
	both modified:   docs/zh/sql-reference/sql-statements/backup_restore/DROP_REPOSITORY.md
	both modified:   docs/zh/sql-reference/sql-statements/backup_restore/RESTORE.md
	both modified:   docs/zh/sql-reference/sql-statements/backup_restore/SHOW_BACKUP.md
	both modified:   docs/zh/sql-reference/sql-statements/backup_restore/SHOW_RESTORE.md
	deleted by them: docs/zh/sql-reference/sql-statements/backup_restore/backup_restore.mdx

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[mergify]

@mergify[bot]: Backport conflict, please reslove the conflict and resubmit the pr