IME refactor - parsing side.

- Moved 3 parsers and associated tests in parsers/input_method
- HierarchyTreeBuilderInputMethod used in all three ime parsers
- Added option in PropertyTreeBuilderFromProto/PropertyTreeNodeFactory to not visit object prototype, as ime protos have defaults in prototype
- Made 'children' property optional in HierarchyTreeBuilder, so we don't have to create a children property for every WM node in ParserWindowManagerUtils

Bug: b/311643292
Test: npm run test:unit:ci
Change-Id: Ie50eb45b3760854d59b9f5c6a22c925284c8984e
20 files changed