Revert "product: Remove wifi-service off SystemServerClassPath"

Revert submission 10103769-load_wifi_service_dynamically

Exempt-From-Owner-Approval: see go/perf-revert-first

Reason for revert: <Regression reported in b/148099857>

Reverted Changes:
I7b658cbfa: SystemServer: Dynamically load wifi-service
I93f2467d0: product: Remove wifi-service off SystemServerClass...

Change-Id: I83a2f93e351675eecc1e15ea1bfd9e1407e3f7cb