This PR improves match compilation: Branch on variables in the order
suggested by the first remaining alternative, and do not branch when the
first remaining alternative does not require it. This fixes
https://github.com/leanprover/lean4/issues/10749. With `set_option
backwards.match.rowMajor false` the old behavior can be turned on.
(For now this is an experiment to get familiar with the code and the
whole
problem domain. It is likely overly naive.)
This PR changes match compilation to reject some pattern matches that
were previously accepted due to inaccessible patterns sometimes treated
like accessible ones. Fixes#10794.
