Because we maintain multiple versions of Terraform across different
release branches, we aim to avoid creating needless differences between
the branches to maximize the chance of successful automatic backporting.
Part of that policy is that we don't make cross-cutting changes to respond
to deprecation of functions in upstream packages and instead we respond
to them gradually over time when we'd be changing the nearby code anyway,
or when new work requires using the replacement APIs.
In recognition of that, this turns of the staticcheck rule that would
otherwise force us to resolve all deprecations before moving forward with
any other change.
Running the tool this way ensures that we'll always run the version
selected by our go.mod file, rather than whatever happened to be available
in $GOPATH/bin on the system where we're running this.
This change caused some contexts to now be using a newer version of
staticcheck with additional checks, and so this commit also includes some
changes to quiet the new warnings without any change in overall behavior.
