Plugins: Track plugin signing errors and expose them to the frontend (#28219) (#28505)

* first pass

* return list

* types and cleanup

* add to plugin page and add styles

* update comment

* update comment

* fix component path

* simplify error component

* simplify error struct

* fix tests

* don't export and fix string()

* update naming

* remove frontend

* introduce phantom loader

* track single error

* remove error from base

* remove unused struct

* remove unnecessary filter

* add errors endpoint

* Update set log to use id field

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

* skip adding BE plugins

* remove errs from plugin + ds list

* remove unnecessary fields

* add signature state to panels

* remove unused code

* apply PR feedback

* update comment

* merge dto with model

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>
(cherry picked from commit 1bee9f4168)

Co-authored-by: Will Browne <wbrowne@users.noreply.github.com>

pkg/plugins/error.go

@@ -0,0 +1,14 @@
+package plugins
+
+const (
+	signatureMissing  ErrorCode = "signatureMissing"
+	signatureModified ErrorCode = "signatureModified"
+	signatureInvalid  ErrorCode = "signatureInvalid"
+)
+
+type ErrorCode string
+
+type PluginError struct {
+	ErrorCode `json:"errorCode"`
+	PluginID  string `json:"pluginId,omitempty"`
+}