[clang-tidy] Added option for disabling const qualifiers in readability-qualified-auto

Summary: Adds an option called `AddConstToQualified` to readability-qualified-auto to toggle adding const to the auto typed pointers and references. By default its enabled but in the LLVM module its disabled.

Reviewers: aaron.ballman, alexfh, JonasToth, hokein, sammccall

Reviewed By: aaron.ballman

Subscribers: Quuxplusone, merge_guards_bot, lebedev.ri, xazax.hun, cfe-commits

Tags: #clang, #clang-tools-extra

Differential Revision: https://reviews.llvm.org/D73548