model object properties as records #3804

Object properties are these weird unnamed struct-like spec types whose fields are referred to as "attributes". See https://tc39.es/ecma262/#sec-object-type. This leads to some awkward phrasing and an inconsistent editorial style across the spec, as can be seen in OrdinaryGetOwnProperty and ValidateAndApplyPropertyDescriptor among others. This is part of our high-level goal of replacing these unusual and ill-defined structures with spec records (#2246, #2288, etc).