nsITabParent is exposed to frontend code and is generally used as a representation of a remote tab. We could just rename the interface to nsIBrowserParent and worry about it later, but I think it's better to rename the interface to nsIRemoteTab so that we can later work on splitting the interface away from the PBrowser protocol.
Note: Some frontend code refers to a TabParentId. This commit renames this to RemoteTabId. We need to figure out the purpose of TabId with fission.
Differential Revision: https://phabricator.services.mozilla.com/D28132
c6e302039f