gh-1111: add redshifts_from_bins()

[ntessore]

Description

Add a new function glass.redshift_from_bins() that allows sampling redshifts from existing tomographic bin labels and redshift distributions.

Closes: #1111

Changelog entry

Added: A new function glass.redshifts_from_bins() to sample redshifts from existing tomographic bin labels and redshift distributions.

Checks

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