Add connected() to API interface (#2580)

* Add connected() to API interface

* Slight doc update

* Align ApiRx

* isConnected() usage

* Updates

* Retrieve isConnected for API via observable

* Remove (now) useless Rx test

packages/rpc-provider/src/http/index.spec.ts

@@ -31,7 +31,7 @@ describe('Http', (): void => {
   });
 
   it('always returns isConnected true', (): void => {
-    expect(http.isConnected()).toEqual(true);
+    expect(http.isConnected).toEqual(true);
   });
 
   it('does not (yet) support subscribe', (): Promise<number | void> => {

packages/rpc-provider/src/http/index.ts

@@ -67,10 +67,17 @@ export default class HttpProvider implements ProviderInterface {
     throw new Error('Unimplemented');
   }
 
+  /**
+   * @description Manually connect from the connection
+   */
+  public async connect (): Promise<void> {
+    // noop
+  }
+
   /**
    * @description Manually disconnect from the connection
    */
-  public disconnect (): void {
+  public async disconnect (): Promise<void> {
     // noop
   }
 
@@ -78,7 +85,7 @@ export default class HttpProvider implements ProviderInterface {
    * @summary Whether the node is connected or not.
    * @return {boolean} true if connected
    */
-  public isConnected (): boolean {
+  public get isConnected (): boolean {
     return true;
   }