IPv6 address validation is inconsistent

While investigating MB-36992 and having the fix for that ticket review, I saw that the way that we validate and parse IPv6 address isn't uniform: when we create a cluster the address is checked in one way, and when we add a node it is checked in another.

Timofey Barmin also raised this point and noted that there's another scenario to be considered:

We should use the same approach in all those dialogs (there is also node addition initiated from node to be added scenario).
I think we can parse it correctly even without brackets when there is no port and no scheme.