TUN-8866: Add linter to cloudflared repository

## Summary
To improve our code, this commit adds a linter that will start
checking for issues from this commit onwards, also forcing
issues to be fixed on the file changed and not only on the changes
themselves. This should help improve our code quality overtime.

Closes TUN-8866

cfsetup.yaml

@@ -13,10 +13,14 @@ bullseye: &bullseye
       - rubygem-fpm
       - rpm
       - libffi-dev
+      - golangci-lint
     pre-cache: &build_pre_cache
       - export GOCACHE=/cfsetup_build/.cache/go-build
       - go install golang.org/x/tools/cmd/goimports@latest
     post-cache:
+      # Linting
+      - make lint
+      - make fmt-check
       # Build binary for component test
       - GOOS=linux GOARCH=amd64 make cloudflared
   build-linux-fips:
@@ -156,7 +160,6 @@ bullseye: &bullseye
       - export GOOS=linux
       - export GOARCH=amd64
       - export PATH="$HOME/go/bin:$PATH"
-      - ./fmt-check.sh
       - make test | gotest-to-teamcity
   test-fips:
     build_dir: *build_dir
@@ -167,7 +170,6 @@ bullseye: &bullseye
       - export GOARCH=amd64
       - export FIPS=true
       - export PATH="$HOME/go/bin:$PATH"
-      - ./fmt-check.sh
       - make test | gotest-to-teamcity
   component-test:
     build_dir: *build_dir