Support postgresql_include for create_primary_key / create_unique_constraint

[anneheartrecord]

Fixes #1723

Problem

postgresql_include (added in SQLAlchemy 2.0.41 for PrimaryKeyConstraint / UniqueConstraint) was only wired up for create_index. Using it via the op directives failed in two distinct ways:

• op.create_primary_key(..., postgresql_include=[...]) raised TypeError: create_primary_key() got an unexpected keyword argument 'postgresql_include' because the public operation method did not accept dialect-specific keyword arguments.
• op.create_unique_constraint(..., postgresql_include=[...]) raised KeyError during DDL compilation: SQLAlchemy's _define_include looks the INCLUDE columns up in constraint.table.c, but those columns are not present on the synthetic table Alembic builds for the ALTER ... ADD CONSTRAINT statement.

Fix

• CreatePrimaryKeyOp.create_primary_key now accepts **kw, so dialect-specific kwargs flow through to the constraint (the rest of the op pipeline — __init__, to_constraint, from_constraint, and SchemaObjects.primary_key_constraint — already passed them through). create_unique_constraint already accepted **kw.
• PostgresqlImpl.add_constraint now appends any postgresql_include columns referenced by name to the constraint's synthetic table before emitting AddConstraint, mirroring the existing handling in create_index. The shared logic is extracted into a small _ensure_include_columns helper used by both create_index and add_constraint.
• Regenerated the .pyi / base.py operation stubs via tools/write_pyi.py (validated by tests/test_stubs.py).
• Added a changelog fragment at docs/build/unreleased/1723.rst.

Tests

Added test_create_unique_constraint_postgresql_include and test_create_primary_key_postgresql_include to tests/test_postgresql.py, asserting the emitted DDL:

ALTER TABLE t ADD CONSTRAINT uq_t UNIQUE (c1, c2) INCLUDE (inc)
ALTER TABLE t ADD CONSTRAINT pk_t PRIMARY KEY (c1, c2) INCLUDE (inc)

Both fail on main (TypeError / KeyError respectively) and pass with this change. Full suite: 1769 passed, 129 skipped (DB-specific). flake8, black, mypy, and the stub-consistency test all pass.