Use staticcheck that goes as part of golangci-lint

This one turned a bit more involved.

Apparently, per golangci/golangci-lint#2017
staticcheck is split into four (!) linters under golangci-lit. These
are: `staticcheck`, `gosimple`, `stylecheck` and `unused`. Using the
same name `staticcheck` for one of linters is not confusing at all.

Anyway, to get full staiccheck's power, one must enable all four
linters in `.golangci.yml`.

With that we can throw staticcheck target away from `Makefile`.

Verified by omitting `"-ST1000"` in `stylecheck.checks` list and
seeing how `make lint` fails with ST1000 findings.

Unfortunately, I found no way to see log of each linter when it is
executed in golangci-lint context to be able to confirm things more
precisely. :-( Looks like golangci-lint simply does not support that.

.golangci.yml

@@ -41,13 +41,22 @@ linters-settings:
       - emptyStringTest
       - hugeParam
       - rangeValCopy
+  gosimple:
+    go: "1.16"
+    checks: ["all"]
   nolintlint:
     allow-leading-space: false # require machine-readable nolint directives (i.e. with no leading space)
     allow-unused: false # report any unused nolint directives
     require-explanation: false # don't require an explanation for nolint directives
     require-specific: true # require nolint directives to be specific about which linter is being skipped
   revive:
     min-confidence: 0
+  staticcheck:
+    go: "1.16"
+    checks: ["all"]
+  stylecheck:
+    go: "1.16"
+    checks: ["all", "-ST1000"]
 
 linters:
   # please, do not use `enable-all`: it's deprecated and will be removed soon.
@@ -91,14 +100,14 @@ linters:
     - revive
     - rowserrcheck
     # - scopelint
-    # - staticcheck
+    - staticcheck
     # - structcheck
-    # - stylecheck
+    - stylecheck
     # - testpackage
     # - typecheck
     - unconvert
     - unparam
-    # - unused
+    - unused
     # - varcheck
     # - whitespace
     # - wsl

Makefile

@@ -40,11 +40,6 @@ $(GOLANGCILINT_BIN): deps
 	@echo "+ $@"
 	go install github.com/golangci/golangci-lint/cmd/golangci-lint
 
-STATICCHECK_BIN := $(GOBIN)/staticcheck
-$(STATICCHECK_BIN): deps
-	@echo "+ $@"
-	go install honnef.co/go/tools/cmd/staticcheck
-
 ###########
 ## Lint ##
 ###########
@@ -60,12 +55,8 @@ else
 	golangci-lint run --fix
 endif
 
-.PHONY: staticcheck
-staticcheck: $(STATICCHECK_BIN)
-	staticcheck -checks=all,-ST1000 ./...
-
 .PHONY: lint
-lint: golangci-lint staticcheck
+lint: golangci-lint
 
 ####################
 ## Code generation #