regexp/no-invalid-regexp for invalid regexes

[RunDevelopment]

Motivation
While developing #282, I noticed that ESLint's no-invalid-regexp only validates expression of the form RegExp(<string literal>). It doesn't support the concatenation of string literals and all the fancy stuff #282 can do.

E.g. ESLint's no-invalid-regexp will detect RegExp("([") but it can't detect RegExp("([" + ""). We can detect this, so why not report it?

Description
Add a new rule regexp/no-invalid-regexp that behaves like ESLint no-invalid-regexp but uses PatternSource under the hood.

The best way to implement this might be to extend the defineRegexpVisitor to allow a new visitor type that doesn't require a parsed RegExpp AST.

Examples

/* ✓ GOOD */
var foo = RegExp("foo")
var foo = RegExp("([" + "])")

/* ✗ BAD */
var foo = RegExp("([")
var foo = new RegExp("([" + "\\" + "])", "i")

[RunDevelopment]

This is blocked by #282. (obviously)

[ota-meshi]

That rule sounds good to me!