cmd/tsconnect: allow SSH username to be specified

Redoes the UI to be a form, with a username field and a host drop-down.

Fixes #5139

Signed-off-by: Mihai Parparita <mihai@tailscale.com>

cmd/tsconnect/src/wasm_js.ts

@@ -17,11 +17,14 @@ declare global {
     logout(): void
     ssh(
       host: string,
-      writeFn: (data: string) => void,
-      setReadFn: (readFn: (data: string) => void) => void,
-      rows: number,
-      cols: number,
-      onDone: () => void
+      username: string,
+      termConfig: {
+        writeFn: (data: string) => void
+        setReadFn: (readFn: (data: string) => void) => void
+        rows: number
+        cols: number
+        onDone: () => void
+      }
     ): void
   }