Move VarType out of its respective outer classes.

It's used more than I originally thought it would be and it's
unnecessarily nested.

Test: rm -rf out/config/ && m product-config-test product-config && java -jar out/host/linux-x86/testcases/product-config-test/product-config-test.jar && time ( product-config --ckati_bin /source/kati/ckati > ~/Desktop/out.txt )
Change-Id: Id5a075863151e37ec60e5d9dbeb817c2df245bc7