This PR update to Go 1.18.2. Also update the versions of hclfmt
and go-hclogfmt which includes newer dependencies necessary for dealing
with go1.18.

The hcl v2 branch is now 'nomad-v2.9.1+tweaks2', to include a fix for
newer macOS versions: https://github.com/hashicorp/hcl/commit/8927e75e82c19370aabaf06b7dca91c2c9e73e3c