Replace Socket, ServerSocket, and HttpServer usages in tests with mocksocket versions

[Tim-Brooks]

This is related to #22116. In order to remove SocketPermissions from core we need to isolate some code that can be given SocketPermissions. The mocksocket jar includes wrapped versions of Socket and SocketServer. This is one step towards migrating permissions out of core.

[Tim-Brooks]

This is currently blocked from being merged on a release of the mocksocket project.

I should get to today or tomorrow.

[s1monw]

this PR LGTM provided MockSocket is available publicially

[jasontedor]

I left one comment.

[jasontedor]

My only comment is whether or not this should be in another package like org.elasticsearch.mocksocket? In general we should avoid split packages, and in a JDK 9 world, split packages are a thing that we are definitely not going to want to do. What do you think @s1monw?

[s1monw]

I don't follow, what do you mean by split packages? this is unrelated to this PR no? I mean we need to fix this in MockSocket? Y

[jasontedor]

Split packages are packages that live in two jars. Yes, it needs to be fixed in mocksocket but this seemed a good place to raise the conversation.

[Tim-Brooks]

I made a few changes to this PR:

1. I placed the classes in a mocksocket package to attempt to address @jasontedor's concern.
2. I added wrappers for HttpServer and HttpsServer. This addresses the problem where those classes do not wrap accept() in doPrivilege().

The mocksocket project is in MavenCentral. So once this passes an updated review, it should be good to merge in.

[Tim-Brooks]

I updated this PR with a new version of mocksocket that adds a method needed for "connect" permissions.

And I rebased it on current master.

[s1monw]

LGTM

[jasontedor]

LGTM.