Extend constraints

#NCS2022

1) constrain ~on continuous variable~ the order of one variable (e.g. sequential dilution on plate)
2) constrain on plates (e.g. pipetting sequence, alternating order or blocks, etc)
(these are almost the same problem)

The issue gives no file, test, or entry point. Start by locating the existing constraint implementation and its tests, then determine how continuous-variable ordering and plate-level sequencing should be represented. Done should include agreed behavior for both constraint categories and tests covering the requested examples.

Written by the indexing model from the issue text.