Recommend ICU replacements, no clone, no Impl.

When ICU has a better replacement class, recommend that APIs use
that instead.

Yell if someone implements clone(), and point them towards a copy
constructor instead.

Yell if someone exposes "Impl" classes.

Test: manual
Bug: 73392214, 71906588, 62627348
Change-Id: I75dcba2c4ab7ca426057eefb0335c935c3ced79a