feat: allow passing Path Parameters as handler parameters

[francescovallone]

Description

Right now the only reference to the path parameters is inside the RequestContext. This feature aims to allow a second type of access to them using the function parameters.

Example:
on(Route.get('/<id>'), (RequestContext context, String id) async => id)

This syntax should be allowed after the merge of this feature.

Requirements

• Allow to pass path parameters as function parameters;
• The function parameters are only positional, not named or optional;
• The parameters must be still accessible from the context to ensure that the hooks and everything else works correctly;