Expand reporting for prefer-node-remove

[brettz9]

• prefer-node-remove: Expand reporting to cover cases where parent of removeChild is other than parentNode or parentElement.

Fixes #506.

[fisker]

@brettz9 Let's focus on prefer-node-remove, do the selector thing on other rule in another PR, shall we?

We have a lot to do with this rule

[fisker]

More detail: #506

@brettz9 already did:

• prefer-node-remove: Expand reporting to cover cases where parent of removeChild is other than parentNode or parentElement.

I've done:

• replace error message with a general message Prefer `childNode.remove()` over `parentNode.removeChild(childNode)`., old one is more specific, but could be Prefer `foo.remove()` over `null.removeChild(foo)`. in some case
• since we are not checking parentNode/parentElement anymore, I removed most of them from tests
• simplify tests that can't be fixed.
• exclude parentNode.removeChild(undefined) -> undefined.remove()

Need to do (will raise another issue after this merge):

• allow more childNode, not only Identifier and ThisExpression, what I most want support is:

parentNode.removeChild(some.node) / parentNode.removeChild(get.child())

• investigate what should we do with complicated callee

eg:

doSomething1().doSomething2().doSomething3().doSomething4().getParent()
	.removeChild(childNode)

we can't just fix to childNode.remove().

/cc @brettz9 @sindresorhus