[ArgPromo][Tests] Run update_test_checks on all ArgumentPromotion tests

Summary:
In preparation of D65531 as well as the reuse of these tests for the
Attributor, we modernize them and use the update_test_checks to simplify
updates.

This was done with the update_test_checks after D68819 and D68850.

Reviewers: hfinkel, vsk, dblaikie, davidxl, tejohnson, tstellar, echristo, chandlerc, efriedma, lebedev.ri

Subscribers: bollu, arphaman, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D68766