all: migrate to github.com/sourcegraph/sourcegraph/lib/errors
Created by: bobheadxi
Migrates all errors in src-cli
to use the new error types introduced in https://github.com/sourcegraph/sourcegraph/pull/31466, and bans further imports of other error libraries.
Some benefits of this migration is that wrapped multierrors no longer obscure child errors, assertions work more consistently, and there is now an overall more ergonomic API for multierrors - see https://github.com/sourcegraph/sourcegraph/pull/31466 for more details.