We improve the approximate order of a stream whenever Stream_inexact.__getitem__ is called.

This may slow down Stream_inexact.__getitem__ but should speed up other operations.

It must be checked carefully whether this is an overall improvement or not.

Depends on #34552

CC: @tscrim

Component: combinatorics

Keywords: LazyPowerSeries

Author: Martin Rubey

Branch/Commit: u/mantepse/improve_approximate_order_on___getitem___calls @ 5a2cb8b

Issue created by migration from https://trac.sagemath.org/ticket/34556