Make retrieving subdomain zones possible and allow 63 char TLDs

Thomrequested to merge
thom/ispconfig3:4522-sub-regex into develop

Closes #4522 (closed)

Allows 63 char TLDs (this change has been added for all other places where we have domain names in !1028 (merged))

Removes the backport needed label from !774 (merged)

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