[GlobalISel][InstructionSelect] Sorting MatchTable's 2nd level by root LLT, perf patch 7

This patch continues a series of patches started by r332907 (reapplied
as r332917).

In this commit we sort rules within their 2nd level by the type check
on def operand of the root instruction, which allows for better
nesting grouping on the level.

This is expected to decrease time GlobalISel spends in its
InstructionSelect pass by roughly 22% for an -O0 build as measured on
sqlite3-amalgamation (http://sqlite.org/download.html) targeting
AArch64 (cross-compile on x86).

Reviewers: qcolombet, dsanders, bogner, aemerson, javed.absar

Reviewed By: qcolombet

Subscribers: rovka, llvm-commits, kristof.beyls

Differential Revision: https://reviews.llvm.org/D44700

llvm-svn: 333131