Add signature matching for positional parameters

[vinistock]

Motivation

Step towards #2363

To determine which signature overload to show, we are going to need to match a declaration signature to the arguments of a method call. Doing it all in a single PR felt a bit too complex, so this PR only adds the method matches? to Signature and only implements matching for positional arguments. I will follow up with the implementation for keyword arguments.

Implementation

For matching positional arguments, we essentially need to check if the number of arguments in the method call are within the range of possible arguments that the method accepts. For example:

def bar(a, b = 2)
end

# The range for valid calls here is 1..2 because you can call `bar` with 1 or 2 arguments
bar(1) # ok!
bar(1, 2) # ok!

There are also special rules for splats and forwarding arguments. In general, these are not statically analyzable and we just bail out saying that the signature does match, but there are a few scenarios where we can do at least partial matching. For example:

def bar(a, *b)
end

# We can't statically analyze anything related to the splat parameter, but we know
# that `bar` requires at least one positional parameter. In this case, the range is
# 1..INFINITY

bar # not ok!
bar(1) # ok!
bar(1, 2) # ok!
bar(*a) # ok!

See the tests for more examples.

Automated Tests

Added tests.