Object asserts not run by std.objectFieldsEx and std.objectHasEx

[sparkprime]

$ jsonnet -e '{} == {assert false}'
true

[sparkprime]

Decided that std.type, std.length, and all other reflection calls should not check asserts, since they check the set of fields, which are either static, or computed before object creation time.

However {} == { assert false } is strange, also std.manifestJson({ assert false }) == '{}' which is also strange.

This can be addressed by adding a native function to evaluate the assertions, and using it in the implementation of == (which is in Jsonnet) and manifestJson.