Fix Reflect has method signature(s) per issue #10949 initial report

[ghost]

Fixes #10949 As per fix initially proposed when issue was created. We just delete the two 'has' methods and replace with a single 'has' method with the signature fixed with 'PropertyKey' annotation.
This brings Reflect into sync with Proxy handler methods noting that all the other methods in Reflect which accept a 'propKey' argument are already annotated with 'PropertyKey' type.

Note that ECMA-262 7th Edition has removed the 'enumerate' method from Reflect altogether yet it remains in es2015.proxy.d.ts. Whether this should be removed or not to bring 'ProxyHandler' into line with the 7th Edition or not I do not know. I don't otherwise know of any means of marking a method as "deprecated" in TypeScript (but perhaps there is?).

[ghost]

btw. I didn't push up the corresponding built lib file lib/lib.es2015.reflect.d.ts as wasn't sure whether to or not especially as it is generated in the compile process (and didn't seem to be the right thing to do). Just kept it simple for your merge as you will be recompiling anyway.

[mhegazy]

I didn't push up the corresponding built lib file lib/lib.es2015.reflect.d.ts as wasn't sure whether to or not especially as it is generated in the compile process.

thanks!

[mhegazy]

Thanks!