[unbound-method] Support super.foo in constructor

[markfields]

Repro

{
  "rules": {
    "@typescript-eslint/unbound-method": [
            "error",
            {
                "ignoreStatic": true
            }
        ]
  }
}

class BaseClass {
    x: number = 42;
    logThis() { console.log(`x is ${this?.x}`); }
}

class OtherClass extends BaseClass {
    superLogThis: any;
    constructor() {
        super();
        this.superLogThis = super.logThis;  // X - Incorrect eslint error
    }
}

const oc = new OtherClass();
oc.superLogThis();  // Works despite eslint error in constructor

Expected Result
No unbound-method error. In the test case above, oc.superLogThis() correctly prints x is 42.

Actual Result
unbound-method error about super.logThis in OtherClass's constructor.

Additional Info

Versions

package	version
@typescript-eslint/eslint-plugin	2.17.0
@typescript-eslint/parser	2.17.0
TypeScript	3.7.5
ESLint	6.8.0
node	10.19.0
npm	6.13.4

[bradzacher]

This seems like something that's doable. Happy to accept a PR!