Rename libicuuc-host/libicui18n-host to libicuuc/libicui18n

These modules can be named the same between the target and host
libraries, which simplifies references to them, particularly in
Soong.

To prevent accidentally loading the system copy of the library,
we still rename the installed name to be libicu*-host.so. But
modules do not need to know that in order to build against them.

Change-Id: I4735599feb73225b2bea6dee42bbc23118693765