rename: respond_to? ->stubba_respond_to?

[nitishr]

Enhances the clarity of the code by explicitly indicating that the method is related to the stub functionality, which aids in understanding the code's intent.

Key Changes:

1. Method Existence Checks:
   • Renamed ClassMethods::AnyInstance#respond_to? to ClassMethods::AnyInstance#stubba_respond_to? to better reflect its purpose as part of a mocha contract.
   • Mockery#on_stubbing now uses stubba_respond_to? instead of the generic respond_to? to check if an object responds to a method before stubbing it.
   • Added ObjectMethods#stubba_respond_to? to provide a consistent interface for checking if an object responds to a method.
2. RuboCop Configuration Updates: Moved test-specific RuboCop rules from the global .rubocop.yml to a new test/.rubocop.yml file (as suggested in commits e423977, 33e373c, fddebc3).

Closes #713.

[floehopper]

Many thanks for taking the time to submit this PR and the other ones!

Enhances the clarity of the code by explicitly indicating that the method is related to the stub functionality, which aids in understanding the code's intent.

Key Changes:

1. **Method Existence Checks:**
   
   * Renamed `ClassMethods::AnyInstance#respond_to?`  to `ClassMethods::AnyInstance#stubba_respond_to?` to better reflect its purpose as part of a mocha contract.

While I'm not vehemently opposed to the new name in the short term, I'm keen to move away from the use of "stubba" all together in the longer term as per #360. However, the new name probably does make sense in the context of the current code. I just wanted to flag this longer-term desire!

   * `Mockery#on_stubbing` now uses `stubba_respond_to?` instead of the generic `respond_to?` to check if an object responds to a method before stubbing it.
   * Added `ObjectMethods#stubba_respond_to?` to provide a consistent interface for checking if an object responds to a method.

Can you explain a bit about why you think this approach is better than definingClassMethods::AnyInstance#respond_to_missing? instead of #respond_to? as suggested in #713? It might well be better, I've just lost track of why I wrote #713 the way I did!

2. **RuboCop Configuration Updates:** Moved test-specific RuboCop rules from the global .rubocop.yml to a new test/.rubocop.yml file (as suggested in commits [e423977](https://github.com/freerange/mocha/commit/e423977cc9fa6cfc4389252ca34342192891e031), [33e373c](https://github.com/freerange/mocha/commit/33e373ca5aa69061124df72e848f63850214f06d), [fddebc3](https://github.com/freerange/mocha/commit/fddebc3815fe3bba69b24cedc575720196f7c4b6)).

I might have missed someting, bit the changes in point 2 feel somewhat orthogonal to the changes in point 1. If so, I'd prefer to have them in a separate PR.