Add support for non-Latin scripts to wordBoundaryPattern

Replacing [a-zA-Z] with a long unicode expression which encompasses
all the characters in the unicode 'letters' category. Similarly replacing
[0-9] with an expression for 'numbers'.

Bug: 44085
Change-Id: Idd403339caa24769ce08133dda06ab6d4b9d694e
Merge "Add support for non-Latin scripts to wordBoundaryPattern"