Test mangled properties

[lbialy]

Codegen mangles property names that are in the set of reserved keywords for both JVM, Scala and Pulumi (wait, notify, given, urn, id, etc). These properties are generated with a following underscore so: notify_, urn_. We need to implement identical logic (probably via a separate module?) for mangling and demangling between codegen and core and use it in ResourceDecoder field lookup.

[lbialy]

Needs some tests.