Revert "Prepare to make InputMethodUtils package-private"

This reverts commit 16703c4b.

Reason for revert:
Just realized that this was not the best approach.

We could already make LocaleUtils package-private too before this CL.
So the right approach was moving these methods to new Java class(es)
instead of moving these methods to LocaleUtils.

Bug: 77730201
Bug: 114660660
Test: atest CtsInputMethodTestCases CtsInputMethodServiceHostTestCases
Test: atest FrameworksCoreTests:com.android.internal.inputmethod
Change-Id: I29c87b9692f0f5e8255835579e2fb5270bc6c9c3