[LayoutlibLoader] Allow to skip ICU / Keyboard initialization

ICU and keyboard configuration parameters are passed from the Java side
using java properties.

We now skip these initializations if the properties are "**n/a**",
and do this on Ravenwood, where ICU and keyboard couldn't be initialized
as of now.

We use a magic value "**n/a**" rather than "", in case "" is already
special cased somehow somewhere.

Bug: 318393625
Test: tree hugger
Test: Tested on the ravenwood prototype branch
Change-Id: Ib3e8925222daf4f092ecf391fe70999a91edd6c0