Update reference to uncrustify and clang-format.
Correct some copy-paste errors. Consolidate some references to
formatting tools and continue to transition away from uncrustify.
uncrustify references and infrastructure remain, along with Jenkins
documentation. These can be removed after transitioning from Jenkins to
GitLab Runner, pending clarification on how to distinguish between
documentation for all supported versions versus the current version.
There are also various references and workarounds related to uncrustify
in the source code. These can be updated in separate changes against the
post-release-2020 master branch.
Refs #3248
Change-Id: I3331f73921812a918d32dd6a045eabc4da4a6a6d