Use go/packages instead of x/tools/loader: it allows to work
with go modules and speedups loading of packages with the help
of build cache.
A lot of linters became "fast": they are enabled by --fast now and
work in 1-2 seconds. Only unparam, interfacer and megacheck
are "slow" linters now.
Average project is analyzed 20-40% faster than before if all linters are
enabled! If we enable all linters except unparam, interfacer and
megacheck analysis is 10-20x faster!
A recent change was introduced in goimports improving how it sort and
format imports in https://go-review.googlesource.com/c/tools/+/116795
This commit updates the vendored version of the golang.org/x/tools
repository to include these changes.
1. Support unparam linter and fix found issues
2. Replace forked mvdan.cc/lint and mvdan.cc/interfacer with the
upstream ones
3. Minimize forked megacheck: move the most of it's code to this repo
4. Use golang.org/x/tools/go/ssa import path instead of custom fork
paths
5. In golang.org/x/tools/go/{ssa,callgraph} use changed code from
honnef.co/go/tools
6. Add megacheck.check-unexported option: it found some issues in
the repo, fixed them all
