21722 Extract textrange (affects: text input, cla: yes, platform-linux, platform-windows)

21854 Migrate TextInputPlugin API to TextRange (affects: text input, cla: yes, platform-linux, platform-windows)

21874 Add TextRange::Contains tests spanning base/extent (affects: text input, cla: yes, platform-linux, platform-windows)

21897 Add multi-step input method support for Linux (affects: desktop, affects: text input, cla: yes, needs tests, platform-linux)

21933 Plumb through Dart entrypoint arguments on the Linux embedder (affects: desktop, cla: yes, needs tests, platform-linux)

22007 Fix FlTextInputPlugin tear down (affects: desktop, cla: yes, needs tests, platform-linux, waiting for tree to go green)