✨ Allow deleting all rows from a table

[jnewbery]

The sqlmodel docs explain how to delete a single row from a table.

It's also useful to be able to delete multiple rows (or even all rows) at the same time. See https://stackoverflow.com/questions/76648956/how-to-delete-all-rows-matching-a-condition-using-sqlmodel for example.

session.exec(delete(Table)) works fine, but triggers a type warning:

Pyright: Error: No overloads for "exec" match the provided arguments [reportCallIssue]
Pyright: Error: Argument of type "Delete" cannot be assigned to parameter "statement" of type "SelectOfScalar[_TSelectParam@exec]" in function "exec"
  "Delete" is not assignable to "SelectOfScalar[_TSelectParam@exec]" [reportArgumentType]

Adding an additional overload to Session.exec() allows this syntax to be used.