WIP: Add private Secret Manager Plugins support to plugin platform (#49544)

* Add protobuf config and generated code, and client wrapper

* wire up loading of secretsmanager plugin, using renderer plugin as a model

* update kvstore provider to check if we should use the grpc plugin. return false always in OSS

* add OSS remote plugin check

* refactor wire gen file

* log which secrets manager is being used

* Fix argument types for remote checker

* Turns out if err != nil, then the result is always nil. Return empty values if there is an error.

* remove duplicate import

* Update pkg/services/secrets/kvstore/kvstore.go

Co-authored-by: Marcus Efraimsson <marcus.efraimsson@gmail.com>

* Update pkg/services/secrets/kvstore/kvstore.go

Co-authored-by: Marcus Efraimsson <marcus.efraimsson@gmail.com>

* refactor RemotePluginCheck interface to just return the Plugin client directly

* rename struct to something less silly

* Update pkg/plugins/backendplugin/secretsmanagerplugin/secretsmanager.proto

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

Co-authored-by: Marcus Efraimsson <marcus.efraimsson@gmail.com>
Co-authored-by: Will Browne <wbrowne@users.noreply.github.com>

pkg/plugins/ifaces.go

@@ -47,6 +47,11 @@ type RendererManager interface {
 	Renderer() *Plugin
 }
 
+type SecretsPluginManager interface {
+	// SecretsManager returns a secretsmanager plugin
+	SecretsManager() *Plugin
+}
+
 type StaticRouteResolver interface {
 	Routes() []*StaticRoute
 }