This commit moves logical step higher than weakest precondition. This
allows the logical step to be used in Iris projects that do not use the standard weakest precondition.
- Moved logical_step.v from program_logic to base_logic
- Move weakest precondition rules for logical step to weakestpre.v
- Added ElimModal instances for logical step w.r.t. physical step, logical step and weakest precondition
- Remove the 'wp_use_step_strong' lemma as it is the same as 'wp_step_update_strong'
These changes were applied to use logical_step in Perennial