Use llvm::is_contained where appropriate (NFC)
Summary:
This patch replaces std::find with llvm::is_contained where
appropriate.
Reviewers: efriedma, nhaehnle
Reviewed By: nhaehnle
Subscribers: arsenm, jvesely, nhaehnle, hiraditya, rogfer01, kerbowa, llvm-commits, vkmr
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D84489