[Functionalization] Lower *view*_scatter ops properly

[alanwaketan]

All scatter ops are written in a way that reuses our view infrastructure, and we need to convert them into proper scatter ops that are without the view infrastructure. Looks like we can directly apply ViewUpdate ops listed here to do a 1:1 mapping. Jiewen tried AsStridedViewUpdate and it passed TestViewOpsXLA.test_as_strided_inplace_view_xla and TestViewOpsXLA.test_as_strided_view_xla tests.

• as_strided_scatter (@alanwaketan, [Functionalization] Lower as_strided_scatter properly #4770)
• diagonal_scatter (@alanwaketan, [Functionalization] Lower diagonal_scatter properly #4784)
• select_scatter (@wonjoolee95, Properly lower select_scatter #4793)
• slice_scatter (@alanwaketan, [Functionalization] Properly lower slice_scatter #4791)

[alanwaketan]

Close this issue as all tasks are completed.