[llvm-exegesis] Print the whole snippet in analysis.

Summary:
On hover, the whole asm snippet is displayed, including operands.

This requires the actual assembly output instead of just the MCInsts:
This is because some pseudo-instructions get lowered to actual target
instructions during codegen (e.g. ABS_Fp32 -> SSE or X87).

Reviewers: gchatelet

Subscribers: mgorny, tschuett, llvm-commits

Differential Revision: https://reviews.llvm.org/D48164

llvm-svn: 334805