Socket connect no longer synchronous and blocking

Summary:
Never really liked this code. Before this change, calls to connect were blocking.

Because of this, we had to make use of promises and a bit of really not that good-looking code.

So, this change makes connect non-blocking meaning that we make full use of our event handler.

These changes contain:
- CSR is not getting generated after each failed attempt.
- Connect is no longer blocking.
- Do not report events via the handler when explicitly disconnecting.

Reviewed By: jknoxville

Differential Revision: D46853228

fbshipit-source-id: 00e6a9c7c039a756175fe14982959e078d92bacb

xplat/Flipper/ConnectionContextStore.h

@@ -57,11 +57,18 @@ class ConnectionContextStore {
    */
   std::pair<std::string, std::string> getCertificate();
 
+  /** Is there a CSR present.
+   */
+  bool hasCertificateSigningRequest() const;
+  /** Is there a client certificate present.
+   */
+  bool hasClientCertificate() const;
+
  private:
   DeviceData deviceData_;
-  std::string csr = "";
+  std::string csr_ = "";
 
-  std::string absoluteFilePath(const char* filename);
+  std::string absoluteFilePath(const char* filename) const;
 };
 
 } // namespace flipper