- fixed copy-tests
- fixed deepcopy attrs in dios

function calls. Instead of copying the entire dios, we now only
store the values we actually masked and their `iloc`-position.
This has the same worst-case-costs (i.e. all values are subject
to masking) but results in significantly cheaper average costs
(i.e. only a small subset of values are subject to masking)

set flags at all (i.e. through early returns) or only UNTOUCHED
flags. This breaks the positional flagging scheme, which should
have one digit for every funtion applied.

the previous implementation, would only mark the start and end point(s) of a constant plateaus if it is as big as window or larger.