Refactor options converter logic

Moved default converters from parser implementation to Converters. Moved other helpers to OptionsData. Also factored out new function getFieldSingularType.

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PiperOrigin-RevId: 150473455
MOS_MIGRATED_REVID=150473455

GitOrigin-RevId: 097e64c412c6a4162a22880fd435ef4632878406
Change-Id: Ife5702b6f39415a7df3fd8b44c1867145a6ac466
4 files changed
tree: 304ecae2ad99bf2f25950bd18087937db03414b6
  1. java/