Now asks for the project folder first, so it can determine a unique project name for creation should the pre-filled name be accepted within the corresponding dialog.
Project name determination only occurs for the initial, pre-filled name suggestion and will not apply if a different name is entered entirely.
Fixes #2989.

Project name pre-filling now always ends in a number (eg. `my_project_1`, `my_project_2`) rather than using a file copy duplication style (eg. `my_project`, `my_project_1`).
In-place error during project naming should a directory with the specified name already exist. This negates the need of having to reinvoke the  create project command to begin creating a project again.

Replaces multiple fsPath() calls with a variable counterpart.