fix: handle workspace.agent and agent.workspace.owner in coder ssh (#18093)

Closes #18088.

The linked issue is misleading -- `coder config-ssh` continues to support the `coder.` prefix. The reason the command
`ssh coder.workspace.agent` fails is because `coder ssh workspace.agent` wasn't supported. This PR fixes that.

We know we used to support `workspace.agent`, as this is what we recommend in the Web UI:
![image](https://github.com/user-attachments/assets/702bbbc7-c586-4947-98a6-4508a481280b)

This PR also adds support for `coder ssh agent.workspace.owner`, such that after running `coder config-ssh`, a command like
```
ssh agent.workspace.owner.coder
```
works, even without Coder Connect running. This is done for parity with an existing workflow that uses `ssh workspace.coder`, which either uses Coder Connect if available, or the CLI.

cli/ssh_test.go

@@ -107,12 +107,14 @@ func TestSSH(t *testing.T) {
 
 		cases := []string{
 			"myworkspace",
+			"myworkspace.dev",
 			"myuser/myworkspace",
 			"myuser--myworkspace",
 			"myuser/myworkspace--dev",
 			"myuser/myworkspace.dev",
 			"myuser--myworkspace--dev",
 			"myuser--myworkspace.dev",
+			"dev.myworkspace.myuser",
 		}
 
 		for _, tc := range cases {