bytes, strings: add cross-references in docstrings
For newly funcs SplitSeq, SplitAfterSeq, FieldsSeq, FieldsFuncSeq.
Updates #61901.
Change-Id: I3c97bfd9c2250de68aaea348c82a05635ee797af
Reviewed-on: https://go-review.googlesource.com/c/go/+/637176
Auto-Submit: Ian Lance Taylor <iant@google.com> Reviewed-by: Robert Griesemer <gri@google.com> Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>