make: move all test deps to a separate module

1. This means those deps don't get pulled in unless we actually need to test.
2. It means we can cordon all the golangci-lint module replace hacks off into a
   separate package.

go.mod

@@ -3,7 +3,6 @@ module github.com/ipfs/go-ipfs
 require (
 	bazil.org/fuse v0.0.0-20180421153158-65cc252bf669
 	github.com/AndreasBriese/bbloom v0.0.0-20190823232136-616930265c33 // indirect
-	github.com/Kubuxu/gocovmerge v0.0.0-20161216165753-7ecaa51963cd
 	github.com/blang/semver v3.5.1+incompatible
 	github.com/bren2010/proquint v0.0.0-20160323162903-38337c27106d
 	github.com/dustin/go-humanize v1.0.0
@@ -12,7 +11,6 @@ require (
 	github.com/fsnotify/fsnotify v1.4.7
 	github.com/go-bindata/go-bindata v3.1.1+incompatible
 	github.com/gogo/protobuf v1.2.1
-	github.com/golangci/golangci-lint v1.17.1
 	github.com/hashicorp/go-multierror v1.0.0
 	github.com/hashicorp/golang-lru v0.5.3
 	github.com/ipfs/go-bitswap v0.1.8
@@ -52,13 +50,9 @@ require (
 	github.com/ipfs/go-path v0.0.7
 	github.com/ipfs/go-unixfs v0.2.1
 	github.com/ipfs/go-verifcid v0.0.1
-	github.com/ipfs/hang-fds v0.0.1
 	github.com/ipfs/interface-go-ipfs-core v0.2.2
-	github.com/ipfs/iptb v1.4.0
-	github.com/ipfs/iptb-plugins v0.1.0
 	github.com/jbenet/go-is-domain v1.0.2
 	github.com/jbenet/go-random v0.0.0-20190219211222-123a90aedc0c
-	github.com/jbenet/go-random-files v0.0.0-20190219210431-31b3f20ebded
 	github.com/jbenet/go-temp-err-catcher v0.0.0-20150120210811-aac704a3f4f2
 	github.com/jbenet/goprocess v0.1.3
 	github.com/libp2p/go-eventbus v0.1.0 // indirect
@@ -109,13 +103,10 @@ require (
 	go.uber.org/goleak v0.10.0 // indirect
 	go.uber.org/multierr v1.1.0 // indirect
 	go4.org v0.0.0-20190313082347-94abd6928b1d // indirect
+	golang.org/x/sync v0.0.0-20190423024810-112230192c58 // indirect
 	golang.org/x/sys v0.0.0-20190626221950-04f50cda93cb
-	golang.org/x/tools v0.0.0-20190621195816-6e04913cbbac // indirect
 	golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7 // indirect
 	gopkg.in/cheggaaa/pb.v1 v1.0.28
-	gotest.tools/gotestsum v0.3.4
 )
 
-replace github.com/golangci/golangci-lint => github.com/mhutchinson/golangci-lint v1.17.2-0.20190819125825-d18f2136e32b
-
 go 1.12