fix: Freezing of Map values during finalization

[chetan-satpute]

Findings

Map keys are not enumerable properties of the Map object, so the propertyIsEnumerable check does not apply to them. This fails the check in finalizeProperty of src/core/finalize.ts.

Changes

• Added a condition to detect Map objects and uses Map.prototype.has to check for key existence.

Fixes #1119