Modernize multi-sig generation in DSL compilers

[paracycle]

Labelling this as breaking-change since we are removing some methods that used to be publicly exported to DSL compilers.

Motivation

Since Shopify/rbi#284 landed, we have access to a cleaner way to define methods with multiple signatures, but we'd been relying on an older way of doing it via a create_method_with_sigs helper method. This PR cleans this situation up.

Implementation

1. Updated the implementation of create_method to not define any signatures if a block is passed and the parameters and return_type have not been passed. This allows the block to define all the parameters and different return types explicitly.
2. Updated all usages of create_method_with_sigs to use the new create_method based mechanism to do multiple signature definitions.
3. Remove create_method_with_sigs and create_sig methods from the RBI extension methods.

Tests

All existing tests should pass.

[KaanOzkan]

I think we also need to bump the rbi version requirement to include the change, v0.1.10

EDIT: We also have #1960 which is bumping it btw

[KaanOzkan]

Suggested change

	# If there is no block, and the params and return type have not been supplied, then
	# If there is no block, and the params and return type have been supplied, then

[KaanOzkan]

Do you think we should document that multi-sigs will need to supply a block that adds sigs? It might be tough to figure out by looking at this method.

[paracycle]

Tbh, we haven't been documenting any of these methods and people have been using the patterns they see being used elsewhere in these files.

So, I don't know how to even start documenting this method and how it works.

[KaanOzkan]

Was this change from count to method_name.to_s intentional?

[paracycle]

Yes, it was, and I actually wanted to do it for other methods as well, but Copilot made many of the changes for me, so I lost steam.

The reason why I want to use method_name.to_s is because it is better for future extension. If there is another method that behaves exactly as count (let's say they add an alias for count), then it will be enough to add that to the where clause, since the method name is dynamic like this.