Simplify Python bindings: remove redundant wrappers and unify variants

- Unify make_constant into make_parameter with optional values arg
- Remove make_const_scalar_mult and make_const_vector_mult (use make_parameter + param variant)
- Unify rel_entr/rel_entr_scalar_vector/rel_entr_vector_scalar into single make_rel_entr with auto-dispatch
- Unify sparse/dense left/right matmul into make_left_matmul/make_right_matmul with format string

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: Transurgeon