Fix issue 11281. Transform parameters with default initializers that
have ids that are also in a parameter with a rest element.
Before, these parameters were not transformed.

Previously, f({...R}, f = R => R) would be incorrectly transformed.

Checking the RHS of an assignment pattern/checking the parent of
an identifier node fails on cases like "({...R}, a = f(R))" or
"({...R}, {[R.key]: a = 42})".

Also refactor tests by removing unecessary tests and
separating "should transform" from "should not transform" tests.