Don't use android::base::StartsWith / EndsWith

These libbase functions now directly pass through to the standard
library. [1] Use the standard library directly, and eliminate this
dependency on libbase.

[1] https://r.android.com/c/platform/system/libbase/+/3315082

Change-Id: I83d79ffa2658f30ae09a7f27cedf14e62b5df41d