[analyzer] StdLibraryFunctionsChecker: Add option to display loaded summaries

Reviewers: NoQ, Szelethus, baloghadamsoftware, balazske

Subscribers: whisperity, xazax.hun, szepet, rnkovacs, a.sidorin, mikhail.ramalho, donat.nagy, dkrupp, gamesh411, Charusso, steakhal, ASDenysPetrov, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D78118