Rework Lint/RedundantSafeNavigation to be more safe

[fatkodima]

Closes #8867
Closes #8868

I reworked this to make an offense only when used inside conditions and only for whitelisted methods.

cc @bbatsov @marcandre @natematykiewicz

[marcandre]

Good work.

I would remove nil? from the allowlist, since foo&.nil? is trivially falsey but foo.nil? isn't.

Unlikely, but nil.methods - Object.new.methods #=> [:to_h, :&, :to_c, :to_f, :to_i, :to_a, :to_r, :rationalize, :|, :^], so foo&.respond_to?(any_of_these) shouldn't be flagged. Because of this, probably best to mark the autocorrect as unsafe (foo&.respond_to?(variable) can't be autocorrected safely).

[fatkodima]

Good points 👍 Removed nil? and marked as unsafe.

[marcandre]

Great. Would it be difficult to exclude foo&.respond_to?(:to_a) and others, when the argument is a literal symbol corresponding to one of the few methods that NilClass defines that may not be defined on other objects?

[fatkodima]

Updated with suggestion.
This surely was easy, I just was lazy 😄

[marcandre]

Almost ready

[fatkodima]

@marcandre Thank you for all reviews 💪
Updated with your suggestions.

[fatkodima]

Updated with suggestions. Let me know if there is anything else I can improve.

[bbatsov]

Thanks!