X Start of xy/lte-multiru branch

This is draft branch of with my multiRU work kept in working state so that
people could try it out while we are working to finalize the work and merge it.

See https://www.erp5.com/project_section/vifib/forum/ORS--Multi-RUs-support-Bh5lSVnMGl/view?list_start=7&reset=1#2067794788
for context.