chore: Enable more linters

Enable more golangci-lint linters.
* `forbidigo` to stop use of non-logger console printing.
* `goimports` to make sure `import` blocks are formatted nicely.
* `misspell` to catch spelling mistakes.
* `whitespace` to catch whitespace issues.

Signed-off-by: SuperQ <superq@gmail.com>

prometheus.go

@@ -1,15 +1,11 @@
 package kvm
 
 import (
-	"net/http"
-
 	"github.com/prometheus/client_golang/prometheus"
 	versioncollector "github.com/prometheus/client_golang/prometheus/collectors/version"
 	"github.com/prometheus/common/version"
 )
 
-var promHandler http.Handler
-
 func initPrometheus() {
 	// A Prometheus metrics endpoint.
 	version.Version = builtAppVersion