Better support segmentation of features in raw data space

[adamltyson]

There are some problems that would fit this tool, but cannot be performed on downsampled data, such as segmenting out total labelled cell volumes (see image.sc post).

It would be nice to add a simpler way for users to:

• Run a segmentation algorithm of their choice on the raw data
• Load this into to brainglobe-segmentation
• Run analysis of volumes per brain region as with anything else

[imagesc-bot]

This issue has been mentioned on Image.sc Forum. There might be relevant details there:

https://forum.image.sc/t/use-registered-atlases-from-brainreg-for-segmentation-in-imaris/86206/55