[clang] Make -Rpass imply -Rpass=.*

Previously with -Rpass (and friends) we'd have remarks "enabled", but
without an actual regex.

As seen in the test change to line numbers, this can give us better
diagnostics by properly enabling NeedLocTracking with -Rpass.

Reviewed By: dblaikie

Differential Revision: https://reviews.llvm.org/D110201