Require that implemented method signature will be identical to interface/base

[eladb]

Repro:

export interface MyInterface {
  foo(bar: string): void;
}

export class MyClass implements MyInterface {
  foo(bar?: string): void;
}

This will succeed in typescript but fail in languages like Java. jsii should not allow it.

[RomainMuller]

Need to make sure this is still permitted.

[RomainMuller]

Confirmed that jsii actively checks for this and prevents that:

error TS0: jsii-playground.MyCkass#foo changes the optionality of paramerter _bar when implementing jsii-playground.IMyInterface (expected false, found true)