By allowing `transform.smt.constrain_params`'s region to yield SMT-vars,
op instances can declare relationships, through constraints, on incoming
params-as-SMT-vars and outgoing SMT-vars-as-params. This makes it
possible to declare that computations on params should be performed.
The semantics are that the yielded SMT-vars should be from any valid
satisfying assignment/model of the constraints in the region.
Introduces a Transform-dialect SMT-extension so that we can have an op
to express constrains on Transform-dialect params, in particular when
these params are knobs -- see transform.tune.knob -- and can hence be
seen as symbolic variables. This op allows expressing joint constraints
over multiple params/knobs together.
While the op's semantics are clearly defined, per SMTLIB, the interpreted
semantics -- i.e. the `apply()` method -- for now just defaults to failure. In
the future we should support attaching an implementation so that users
can Bring Your Own Solver and thereby control performance of
interpreting the op. For now the main usage is to walk schedule IR and
collect these constraints so that knobs can be rewritten to constants that
satisfy the constraints.
