ICU String Tries

We have several implementations of string tries, mapping strings to boolean or integer values: Currently for time zone name parsing and DBBI. Other areas might also benefit from tries: Property names, character names, UnicodeSetStringSpan, .dat package file TOC.

We should have a small number of common map-from-string trie implementations; fairly compact, fairly efficient, easily serializable, and well-tested.

See the subpages for ideas.

For a UnicodeSetStringSpan, we would want to find each next match starting from some point in the text, rather than passing each unit of text and finding out if the units so far match.

Note: In terms of whole-string-lookup performance, the fastest data structure is a hash map. Where whole-string-lookup is the only relevant operation, we could consider implementing an easily serialized hash map.