Ensuring mode solver fields are returned in requested precision

[momchil-flex]

This was motivated by two things when using the default single precision:

• Smaller file size for download
• Smaller chance of OOM which can sometimes happen for very large mode solves in the post-processing (colocating, normalizing, sorting modes).

[tylerflex]

Looks good to me. I feel like eventually we can move towards using Enum for things like this, but for now it's ok. Maybe along with #564 we can try to use enums internally as well throughout the codebase. @daquinteroflex

[dbochkov-flexcompute]

Looks good to me as well. When slicing data for GUI I convert everything into single precision no matter what's the input to make storage and downloading more efficient, do you think that's ok to keep it that way? (cc: @xin-flex)

[momchil-flex]

Conversely this makes me wonder if we should just always store the mode fields in single precision? The precision argument was added because in some cases it may be important for the mode solve; but casting the final results seems pretty innocuous?

[momchil-flex]

I think using the "least amount of work" razor we can assume both are fine as they are. :D