Create parameter type list based on position instead of name

[vinistock]

Motivation

I was testing out the latest Tapioca main and noticed that we are producing invalid syntax in RBIs for anonymous keyword rest or block parameters (see tests).

We are currently outputting this:

# Note the missing type after the parameter name, which is a syntax error
sig { arg_1: }.void
def foo(**); end

Implementation

The essence of the issue is that we create a hash of parameter types, which we lookup based on names. This only works if the parameter actually has a name.

The idea of the implementation is to rely on the fact that Sorbet errors if parameters are out of order and process them based on their position instead. This allows us to at least produce syntactically valid RBIs under the scenarios.

Tests

Added tests.

[vinistock]

Actually, we should push #2687 forward instead.