add special check for parameter initializer lookup if targeting es2015+

[Kingwl]

Fixes #22769

[ajafff]

I didn't mention this in the original issue, but that's not limited to parameter intializers. It's basically every expression that could occur in a ParameterDeclaration. For example a ComputedPropertyName:

let foo = 0;

(function test({[foo]: bar}: any[]) {
    let foo = 1;
    console.log(bar); // logs 'a'
})(['a', 'b'])

[Kingwl]

This is too desperate🤷‍♂️

[weswigham]

@RyanCavanaugh probably worth noting that even though this is a bugfix, it is also a breaking change. Also, in the context of parameter properties it doesn't make sense (ie, it is wrong), since those will still get downleveled, eg:

class Foo {
    constructor(public x = 12, public y = x.toFixed()) {}
}

we have breaks in RWC along these lines.

[sandersn]

Filed #26719 to track the regression.