feat: Remove init functions from collectors

Behaviour of init functions has been centralised in `collector/init.go`,
and can be called during exporter startup. This allows the exporter to
control the timing of collector initialisation, rather than relying on
the import & `init()` method.

This should reduce unexpected behaviour arising from the use of
`init()`, such as #551.

Signed-off-by: Ben Reedy <breed808@breed808.com>

collector/cpu.go

@@ -9,17 +9,6 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 )
 
-func init() {
-	var deps string
-	// See below for 6.05 magic value
-	if getWindowsVersion() > 6.05 {
-		deps = "Processor Information"
-	} else {
-		deps = "Processor"
-	}
-	registerCollector("cpu", newCPUCollector, deps)
-}
-
 type cpuCollectorBasic struct {
 	CStateSecondsTotal *prometheus.Desc
 	TimeTotal          *prometheus.Desc