fix(ringmapmaker): MPI calls could get out of sync
fix(ringmapmaker): MPI calls could get out of sync

This fixes a nasty bug where MPI calls could get out of sync when using
`DeconvolveAnalyticalBeam` in a case where different ranks have
differing numbers of frequencies. To rectify this it refactors the code
such that the beam_mmodes are generate for all frequencies at once which
will prevent the bug from resurfacing in newer implementations.

radiocosmology/draco,radiocosmology/draco