add option to set cursor capture mode for RDP

When using screen-share-mode extend with RDP it is sometimes desirable to capture the local cursor in the framebuffer rather including as metadata, so that an rdp client can be used as an extra display.

This PR allows the screen cast cursor mode to be set, enabling this functionality if desired as per the issue here. It is tested and working on a locally compiled version in Gnome 43 on Manjaro.

I apologise however.. I am no programmer, merely a humble DevOps engineer - and so I imagine that this implementation is far from perfect(!). I am keen to learn however and would welcome any criticism, guidance, instruction, etc to improve the quality of this PR.

It seems I am not the only one who would like this functionality - evidenced by the conversations below:

https://www.omgubuntu.co.uk/2022/06/use-ipad-as-second-monitor-ubuntu-22-04 https://www.reddit.com/r/gnome/comments/uz5as7/gnome_has_made_it_super_simple_to_extend_your/ https://www.reddit.com/r/kde/comments/v08xg9/using_an_android_tabletipadanother_pc_as_a_second/ https://www.reddit.com/r/GadgeteerZA/comments/vdi4sj/using_a_tablet_as_a_second_monitor_in_ubuntu_is/ https://www.reddit.com/r/gnome/comments/wbvd9v/is_gnomeremotedesktop_broken/