[Docs] Cleanup pass documentation

Currently the pass documentation specifies every pass with a single dash
(-) in front of it as this was the old format for specifying passes with
opt. However, after the transition to the new PM, this syntax is
deprecated. This patch removes all the single dashes from the pass page
to reflect this. Additionally, some previously removed/renamed passes
are removed/updated in the pass list.

Differential Revision: https://reviews.llvm.org/D157656