Cop requests: Merge ActiveRecord's multiple `where` into one

[baado]

Is your feature request related to a problem? Please describe.

e.g. .where(column1: :a).where(column2: :b) -> .where(column1: :a, column2: :b)

Describe the solution you'd like

I'd like to auto fix it, maybe :)

Describe alternatives you've considered

Or, do we ourselves write these cops?

Additional context

I cut one out of #953 issue which describes multiple issues.

Technically, where.not etc need to be taken care of. Can you open this a new separate issue?

commented by @koic

[ktopolski]

Hey @koic , do you need help with this one? I think I'll have couple of hours weekly free to work on OS and I'd be happy to help(with this one or with anything other) 😅

[koic]

Perhaps this is this cop that should be discussed first in the Rails style guide. Please open a proposal with the style guide first: https://github.com/rubocop/rails-style-guide