[Feature Request] new cube_sql property to enhance data blending

I propose adding a cube_sql property to enhance data blending in Cube.js. This feature would allow developers to reference other cubes directly by their identifiers within SQL queries, simplifying syntax and improving readability. Currently, referencing another cube's SQL requires explicit calls to .sql(), adding complexity. The cube_sql property would abstract these details, making cube references more intuitive and streamlining data modeling processes. This could encourage clearer code and ease the learning curve for new users.