Allow to start a remote session from the Web IDE

What does this MR do?

It creates a UI that allows starting a new remote session from the Web IDE. The starting point is a button in an empty terminal view that, when clicked, prompts the user to enter the remote environment parameters. If the user enters all the parameters correctly, the Web IDE broadcasts this information to the parent Frame (i.e. the GitLab application). Otherwise, the Web IDE displays an error message indicating that the user should provide all the required information.

Screenshots