Open Prompt for new scenes

Following all the issues surrounding `Y min/max clip` and `Min/Max Y level` and, considering potential solutions, I believe that opening a `New Scene` prompt/window may help alleviate issues.

Upon using `New scene from selection` OR `Load selected chunks` (only for first usage) we should open a `New Scene` window to ask the user for the following information:

`Scene name` - if blank/unchanged will use "default" naming scheme.

`Y min clip`

`Y max clip`

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We could also bring other key settings forward such as what entities to load, ESS, Octree/BVH to use, etc. Which could act as good reminders to the user to consider these options.

Start by tracing the New scene from selection and first-use Load selected chunks actions to their scene-creation flow. The change is complete when a New Scene window captures the scene name, Y min clip, and Y max clip, with blank or unchanged names using the default naming scheme; the additional settings are optional considerations in the issue.

Written by the indexing model from the issue text.