Review NamedTuple methods

[odersky]

Compiler version

3.6

Minimized example

NamedTuple is leaving @experimental status. Before it can be released as part of 3.6, we should do a last sweep over its methods to see whether we need anything changed.

[WojciechMazur]

Is there anything left to do about Named Tuples before 3.6.0? I can see 1 open PR related to named tuples - #21710

[bishabosha]

Those and PR #21710 were meant to be included in 3.6

[EugeneFlesselle]

Closed with #21710