Add NonEmptyList and NonEmptySeq Helper Functions

[devinlyons]

This PR adds helper functions to the NonEmptyList and NonEmptySeq modules that bring them up to feature parity with the List and Seq modules.

[wallymathieu]

Perhaps the doc-xml is either malformed or requires an update of fsdocs

  System.Xml.XmlException: The 'c' start tag on line 5987 position 77 does not match the end tag of 'summary'. Line 5987, position 143.

From https://github.com/fsprojects/FSharpPlus/actions/runs/11390820294/job/31734854875?pr=610