Add a method to create the insets source ID

InsetsSource#createId takes 3 parematers:
- owner: This is an object. If two processes provides the same type,
         (ex: SystemUI and Launcher both provide Type#navigationBars)
         the sources should be different. And only the owner can
         modify its own source.
- index: An owner may have multiple sources with the same type. Ex:
         the system server might have multiple display cutout sources
         at different sides. This is used to identify each of them.
- type: The InsetsType of the source.

This CL lets the sources of IME and display cutouts use the IDs created
by the new method. Thus, some of ITYPEs are not used anymore and they
are removed since this CL.

This CL also stops using ITYPEs as the source IDs in the unit tests of
the core framework, but uses the IDs created by the new method instead.

Bug: 234093736
Test: atest ImeInsetsSourceConsumerTest InsetsControllerTest
      InsetsSourceConsumerTest InsetsSourceTest InsetsStateTest
      DisplayImeControllerTest ActivityRecordTests
      DisplayPolicyLayoutTests DisplayPolicyTests
      ImeInsetsSourceProviderTest InsetsStateControllerTest
      WindowContainerInsetsSourceProviderTest WindowLayoutTests
      WindowStateTests WindowTokenTests
Change-Id: I1e8514bf820f5ba56e9462aafe51eb9c2b5a1cc6