Remove dependancy of TestHttpServer, HttpTransaction, HttpCallback from open/test/jdk/ tests

There are some regression tests depending on TestHttpServer. internal API dependency should be removed from tests:
open/test/jdk/java/net/ProxySelector/LoopbackAddresses.java
open/test/jdk/java/net/ProxySelector/ProxyTest.java
open/test/jdk/java/net/URL/PerConnectionProxy.java
open/test/jdk/java/net/URLConnection/B5052093.java
open/test/jdk/sun/net/www/AuthHeaderTest.java
open/test/jdk/sun/net/www/http/KeepAliveCache/B5045306.java

These test classes should be removed from test library, as these are replace by standard JDK HttpExchange, HttpServer, HttpHandler classes in test.
open/test/jdk/sun/net/www/httptest/AbstractCallback.java
open/test/jdk/sun/net/www/httptest/ClosedChannelList.java
open/test/jdk/sun/net/www/httptest/HttpCallback.java