Bug 1856267 - Don't use ICU4X segmenter if word is ASCII only and non…

…-breakable character. r=TYLin,jfkthame

`mCurrentWordContainsComplexChar` and `wordHasComplexChar` seem to be used
 whether a word has breakable character. I would like to rename it for clean
up.

Also, `nsLineBreaker` has a fast path if character is ASCII, alphabet (AL) and
number (NU). But IS and QU are also unbreakable. So we should add it by using
simple table.

Differential Revision: https://phabricator.services.mozilla.com/D190379

UltraBlame original commit: d13725dac1c15841e3ae5265ac493e9cb7411dd1