Allow for individual test skiping

It would be awesome if you could turn RBS test on and off for single unit tests.

Given the following example:

class MyClass
  attr_reader :name #: Symbol

  # @rbs (name: String | Symbol) -> void
  def initialize(name:)
    validate_name(name)
    @name = name.to_sym
  end

  private

  # @rbs (untyped name) -> void
  def validate_name(name)
    raise ArgumentError, "Invalid name: #{name}" unless name.is_a?(String) || name.is_a?(Symbol)
  end
end

and the following test:

RSpec.describe MyClass do
  describe '.new' do
    subject(:my_class) { described_class.new(name) }
  
   # RBS test needs to skip this context as we're intentionally violating types here.
    context 'when given an invalid name' do
      let(:name) { 123 }

      it { expect { my_class }.to raise_error(ArgumentError, /Invalid name/) }
    end

    # RBS test should not skip this context
    context 'when given a valid name' do
      let(:name) { 'foo' }

      it { expect { my_class }.not_to raise_error }

      it 'is expected to set the name' do
        expect(my_class).to have_attributes(name: :foo)
      end
    end
  end
end

While it's great that RBS can catch these type errors its only really beneficial if those who use your gem as a dependency are also using RBS on their project. So we still need to write in protections like this but are unable to test them because the test in this example will raise an RBS TypeError. Additionally we don't want to completely turn off RBS for the initialize method with the %a{rbs:test:skip} annotation as it's just this single test that will raise the error.

The obvious work around here is to have the name argument in the initializer be untyped however that reduces the clarity of the signature making the end user believe they may pass whatever they would like for name to the initializer.

Start by tracing how RBS tests process RSpec examples and how the %a{rbs:test:skip} annotation is recognized. Define a per-example opt-out that skips only the invalid-name case while keeping the valid-name checks active, then cover both behaviors with the example scenarios in the issue.