generate v1.26 (#1122)

* update swagger

* remove unused models in converter

* remove netcore3.1 from testr

* bump ver

* fix convert

* remove some unused autorest property

* move some clz from autorest to client

* fix import

* no longer expose SendRequestRaw

* make file utils inner

* fix build

* c# 11

examples/prometheus/Prometheus.cs

@@ -1,5 +1,4 @@
 using k8s;
-using k8s.Monitoring;
 using Prometheus;
 using System;
 using System.Net.Http;