The current API is somewhat confusing at times and simpler usage is
possible. This overloads the arguments further to accept objects
with deprecation codes as property keys. It also adds documentation
for the different possible styles.

Besides that it is now going to validate for the code being present
in case of deprecations but not for other cases. The former validation
was not consistent as it only validated some cases and accepted
undefined instead of `common.NoWarnCode`. This check is removed due to
the lack of consistency.

This also verifies that the warning order is identical to the order
in which they are triggered.

This property was just sugar for `undefined` and did not check much.
Now that we properly check that a DeprecationWarning requires a code
we do not have to check that a code is always present.