Rendering: Adds PDF support behind feature toggle (#81811)

* start pdf refactor

* Update AppChrome.tsx

* Update AppChrome.tsx

* add encoding param to rendering grpc service

* fix plugin mode

* clean up

* fix backend tests

* fix lint errors

* Support pdf encoding in render http api

---------

Co-authored-by: Torkel Ödegaard <torkel@grafana.com>

pkg/plugins/backendplugin/pluginextensionv2/rendererv2_grpc.pb.go

@@ -1,7 +1,7 @@
 // Code generated by protoc-gen-go-grpc. DO NOT EDIT.
 // versions:
 // - protoc-gen-go-grpc v1.3.0
-// - protoc             v4.25.1
+// - protoc             v4.25.2
 // source: rendererv2.proto
 
 package pluginextensionv2