Check return type of functions (opt-in)

[radeusgd]

As discussed in github.com/orgs/enso-org/discussions/5987

The ticket #6166 adds the syntax within the parser for specifying return types on a function like:

foo (arg : Integer) -> Text = "{"+arg.to_text+"}"

This ticket should:

• update TreeToIr to handle the newly added parser construct and record the return type in the IR of the created function;
• update IrToTruffle to add a TypeCheckExpressionNode on the return value of the function.
  • Ensure that the check works well with TCO.