Bug 1389715 - Upgrade to Mercurial 4.3.1. r=ted, a=release

This is pretty straightforward: we just update some version numbers
and hashes.

The tooltool artifacts were produced and uploaded by me, just like
the last ones. I have some patches to establish a proper toolchain
task to build Mercurial. But it is a bit of a rabbit hole due to the
chicken-and-egg problem of Mercurial needing to be in Docker images.
Preserving the existing install mechanism is the simplest path
forward. Plus we need this patch so we can uplift so earlier releases
get a secure Mercurial in their Docker images.

color and pager are enabled by default in 4.2. So remove configuration
options for them that add no value.

MozReview-Commit-ID: 9pkHX044kV8