Create new setting option

[borisbauer-unity]

Description

Added an option on the first welcome layout of PA.

Changes made

• ProjectAuditorWindow has a new "Create New Settings" button with a layout on the right of the settings drop-down
• the "Create New Settings" button action uses the standard save file prompt, saves a new ProjectSettings asset if the requester was not cancelled
• creating a new settings asset selects this asset both as the current PA setting and as the current selected asset in the Editor, i.e. the Inspector (if open/visible) shows the settings right away to the user

Notes

TODO: I could update the docs regarding the settings in this PR, unless we prefer a full pass over the docs at a later time.

[borisbauer-unity]

I found a much better alternative API for new/save file prompts:

A different Unity UI method EditorUtility.SaveFilePanelInProject() ensures that a user only picks a path within Assets.

Note: This API is not fully documented. It features an optional path parameter AND guarantees a returned relative path (relative to Assets/), both in their UX warning the user and what the returned string contains.

[mtrive]

found a little bug:

• Create a New Settings Asset
• Change selection to Default
• Click on the dropdown list

The new settings asset does not appear on the list

[borisbauer-unity]

The new settings asset does not appear on the list

Oh, right, there was not a general refresh so far for that drop-down interaction and at creation time.

Maybe I should add it even for the drop-down action (the drop-down appearing), so it would detect any new asset on disk.