Implement provider meta schema everywher on the client.

We returned the ProviderMeta schema from the client on every protocol
request, but missed it on ReadResource for some reason. This rectifies
that.

plugin/grpc_provider.go

@@ -331,6 +331,7 @@ func (p *GRPCProvider) ReadResource(r providers.ReadResourceRequest) (resp provi
 	log.Printf("[TRACE] GRPCProvider: ReadResource")
 
 	resSchema := p.getResourceSchema(r.TypeName)
+	metaSchema := p.getProviderMetaSchema()
 
 	mp, err := msgpack.Marshal(r.PriorState, resSchema.Block.ImpliedType())
 	if err != nil {
@@ -344,6 +345,15 @@ func (p *GRPCProvider) ReadResource(r providers.ReadResourceRequest) (resp provi
 		Private:      r.Private,
 	}
 
+	if metaSchema.Block != nil {
+		metaMP, err := msgpack.Marshal(r.ProviderMeta, metaSchema.Block.ImpliedType())
+		if err != nil {
+			resp.Diagnostics = resp.Diagnostics.Append(err)
+			return resp
+		}
+		protoReq.ProviderMeta = &proto.DynamicValue{Msgpack: metaMP}
+	}
+
 	protoResp, err := p.client.ReadResource(p.ctx, protoReq)
 	if err != nil {
 		resp.Diagnostics = resp.Diagnostics.Append(err)