Plugins: Use grafana-plugin-sdk-go v0.5.0 (#21116)

* fix dispense

* plugin loading refactor

Moves common functionality of registering, starting,
stopping and restarting backend plugins to
backendplugin package.

* simplify plugin descriptors

* target sdk v0.5.0

Co-authored-by: Kyle Brandt <kyle@kbrandt.com>

vendor/github.com/prometheus/procfs/internal/util/parse.go

@@ -49,6 +49,21 @@ func ParseUint64s(ss []string) ([]uint64, error) {
 	return us, nil
 }
 
+// ParsePInt64s parses a slice of strings into a slice of int64 pointers.
+func ParsePInt64s(ss []string) ([]*int64, error) {
+	us := make([]*int64, 0, len(ss))
+	for _, s := range ss {
+		u, err := strconv.ParseInt(s, 10, 64)
+		if err != nil {
+			return nil, err
+		}
+
+		us = append(us, &u)
+	}
+
+	return us, nil
+}
+
 // ReadUintFromFile reads a file and attempts to parse a uint64 from it.
 func ReadUintFromFile(path string) (uint64, error) {
 	data, err := ioutil.ReadFile(path)
@@ -57,3 +72,17 @@ func ReadUintFromFile(path string) (uint64, error) {
 	}
 	return strconv.ParseUint(strings.TrimSpace(string(data)), 10, 64)
 }
+
+// ParseBool parses a string into a boolean pointer.
+func ParseBool(b string) *bool {
+	var truth bool
+	switch b {
+	case "enabled":
+		truth = true
+	case "disabled":
+		truth = false
+	default:
+		return nil
+	}
+	return &truth
+}