Change of syntax for rise.lambda operation

[martin-luecke]

We will change the syntax of our rise.lambda operation from currently trying to mirror the functional style:

%foo = rise.lambda(%a, %b) : !rise.fun<scalar<f32> -> fun<scalar<f32> -> scalar<f32>>> {...}

to better fit into the SSA world and clarify that the SSA Values specified in the lambda are defined here, not before:

%foo = rise.lambda(%a : !rise.scalar<f32>, %b : scalar<f32>) -> scalar<f32> {...}

Note this lambda still has the same rise function type as above, where it was specified explicitly.

[martin-luecke]

Implemented in a44a65e