[InstSimplify] fold extracting from std::pair (2/2)

This is the second patch of the series which intends to enable jump threading for an inlined method whose return type is std::pair<int, bool> or std::pair<bool, int>. 
The first patch is https://reviews.llvm.org/rL338485.

This patch handles code sequences that merges two values using `shl` and `or`, then extracts one value using `and`.

Differential Revision: https://reviews.llvm.org/D49981

llvm-svn: 338817