[DocsUI] fix SortingCursorWrapper sort algorithm

The previous "Borrowed from TimSort.binarySort(), but modified"
algorithm is buggy. Use java.lang.Arrays.sort instead.

Here are my crude benchmark numbers. Milliseconds, lower is better.

Before: 11, 11, 12, 12, 17
After: 3, 4, 4, 4, 9

Bug: 437258483
Flag: EXEMPT bug fix
Test: atest DocumentsUIGoogleTests:com.android.documentsui.sorting.SortingCursorWrapperTest
Change-Id: If26ad244a614e45d191e13c33c5e9dc76a9097ea