[ADD] (*_)_product_matrix: test tours

addons/product_matrix/tests/__init__.py

addons/product_matrix/tests/common.py

addons/purchase/views/purchase_views.xml

...matrix/static/tests/tours/purchase_product_matrix_tour.js

addons/purchase_product_matrix/tests/__init__.py

addons/purchase_product_matrix/tests/test_purchase_matrix.py

addons/purchase_product_matrix/views/assets.xml

...uct_matrix/static/tests/tours/sale_product_matrix_tour.js

addons/sale_product_matrix/tests/__init__.py

addons/sale_product_matrix/tests/test_sale_matrix.py

addons/sale_product_matrix/views/assets.xml