More improvements to currysrc / srcgen

Focusing on handling ICU JavaDoc tags.

ICU SrcGen:
Adjusted for changes in CurrySrc.
Replaced instances of @icu, @icunote, @icuextended
with appropriate expanded text.
Removed instances of @draft, @provisional, @internal.
Turned of debug.

CurrySrc:
Switched many of the Javadoc manipulation transforms to modify
the AST rather than modifying the Document text directly.
Tidied up various classes, e.g. renaming, making final.

Bug: 22023363
Change-Id: I9390e5e14bdea139bab94f819602f9f9107cb8eb
22 files changed