CI: move grabpl package command to pkg/build (#55651)

* add grabpl package

* update .drone.yml

* resolve lint errors

pkg/build/validation/docs.go

@@ -0,0 +1,2 @@
+// Package validation provides functions and types for validating Grafana releases in both the pre-release and post-release phases.
+package validation

pkg/build/validation/validation.go

@@ -0,0 +1,27 @@
+package validation
+
+import (
+	"context"
+)
+
+type ArtifactType int
+
+const (
+	ArtifactTypeDockerHub ArtifactType = iota
+	ArtifactTypeGCSObject
+)
+
+type Artifact struct {
+	Type ArtifactType
+	URL  string
+}
+
+// ReleaseArtifacts generates a list of release artifacts
+func ReleaseArtifacts(version string) ([]Artifact, error) {
+	return nil, nil
+}
+
+// VerifyRelease tests that a that, given the information, a release will completed wholly and successfully.
+func VerifyRelease(ctx context.Context, version string) (bool, error) {
+	return false, nil
+}