fn split_field(field: &str) -> SmallVec<[String; 2]> ⓘExpand description
Split one event_fields entry into its segments, inverting the MSC3873
escape grammar used by ruma’s escape_key: \. is a literal dot inside the
current segment, \\ a literal backslash, any other \X is kept verbatim,
and an unescaped . ends the segment.