Split ui/base/ime into a new component

Split ui/base/ime into a new component

The IME code in ui/base/ime depends on ui/ozone to support keyboard
control (via the InputController interface). This dependency is
currently missing from the build.

Unfortunately, we cannot simply add this dependency, because ui/ozone
depends on code from ui/base/cursor and ui/base/resource
(for cursor bitmaps).

Break this cycle by componentizing ui/base/ime & add a dependency
from the new ui/base/ime component to ui/ozone.

This also helps clean things up a bit because iOS builds ui/base
but not ui/base/ime. So there is already a fault line here.

The handful of IME tests are left as part of ui_base_unittests.

BUG=445627
TEST=gn gen out_gn_ozone --args='os="chromeos" use_ozone=true is_component_build=true' &&
  ninja -C out_gn_ozone chrome ozone_unittests (along with other needed changes)
TBR=jam

Review URL: https://codereview.chromium.org/889323003

Cr-Commit-Position: refs/heads/master@{#314815}