[REQUEST] Ability to change startup `Lines` value + general QoL enhancements

[Sneakpeakcss]

• It would be good to have an option to set a custom Lines value that will be saved, just to avoid constantly changing it after re-opening mpv.

In the case of Filter, i would say that it's more of a search box rather than a filter, which is most noticeable in console tab, and this brings the second request:

• Currently, changing Level only filters new messages. Would it be possible to allow it to filter already displayed messages based on chosen level? Alternatively, allowing the Filter to search through messages by using corresponding tags (error, warn, info, etc)

• Ability to copy selected lines. Having the whole window draggable is quite convenient, so rather than making the console selectable and losing this, then maybe allowing to make a selection by using shift+click, if that's even possible ?

[tsl0922]

Changed Filter to Search and increased the default Lines value to 5000.

Other requests are not planned, such features are complex to be implemented with imgui.