script server: load script directly from file

As a reflectometry instrument scientist I would like to be able to load a script onto the queue directly from a file without going via "edit script" window, to reduce number of clicks.

This should be a relatively minor extension of the script server GUI, with no server-side changes required.

Contact MS (INTER) when done.

Start by locating the script server GUI and its existing “edit script” queue flow. Confirm the file-loading path and acceptance criteria with MS (INTER); done means a script can be loaded onto the queue directly from a file without opening the edit-script window, with no server-side changes.

Written by the indexing model from the issue text.