Add regex validation for table names in 'bulk_load_custom'

[kdsjZh]

related: #47255

This is a PR to add table name validation for 'bulk_load_custom', as an followup for incomplete fix in PR #47255.

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[kdsjZh]

Hi, the second commit is a hardening for an incomplete fix in #48098.

[eladkal]

can you extract the google changes to separated PR?
We generate release notes from the commit message and the commit message is for mysql only

[kdsjZh]

I revoke the second change and will update the second hard in a separate PR.

[github-actions]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed in 5 days if no further activity occurs. Thank you for your contributions.