vim: Extra textobjects + minor changes and tests

[hrou0003]

• Added textobjects.scm for core and extension languages (didn't implement inheritance)
• Tests
• Implemented class motion by turning method_motion into text_object_motion and taking in a TextObject

Release Notes:

• N/A

[xdBronch]

unless im misunderstanding the purpose i dont think any of these are right except params and comments. function.inside is gonna match the parameters, test.inside is gonna match the test name if it has one, and all the class.insides are gonna match the first field or type modifiers like the u32 in enum(u32)

[ConradIrwin]

@hrou0003 thank you for this! Sorry I was also working on this at the same time, and it's all changed quite a bit since when your PR was based on.

I am going to have to close this. I was planning to work on extension languages today too.