Allow built-in `IPv{4,6}Address` objects when constructing A/AAAA rdata (#1183)

Allow built-in `IPv{4,6}Address` objects when constructing A/AAAA rdata (#1183)

* Allow built-in IPv{4,6}Address objects when constructing A/AAAA rdata

Also applies elsewhere where dns.rdata.Rdata._as_ipv{4,6}_address is
used.

* Typecheck `tok` argument in dns.rdata.from_text

This now returns a better error message. Previously:

`SyntaxError: 'foo' object has no attribute 'get'`

Now:

`ValueError: tok must be a string or a Tokenizer`

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Co-authored-by: Štěpán Balážik <stepan@isc.org>