Add prebuilt_systemserverclasspath_fragment rule.

This is the prebuilt side of systemserverclasspath_fragment, currently
for used for dexpreopting.

The change to automactially generate
prebuilt_systemserverclasspath_fragment rules will be in a separate CL.

Bug: 194150908
Test: m nothing
Change-Id: Ibf5322f80f78ac3ca037489f4a279456fe38a23f