patch 9.1.1090: tests: test_terminwscroll_topline2 unreliable

patch 9.1.1090: tests: test_terminwscroll_topline2 unreliable

Problem:  tests: test_terminwscroll_topline2 unreliable
          (Yee Cheng Chin)
Solution: instead of using term_wait() with a specific time, use
          terminal-api and to wait until the terminal is finished

call a terminal callback function when finished printing, instead of
using term_wait(), with a defined time, which caused timeouts on CI
with the macos runners

Unfortunately I couldn't figure out how to call the terminal-api on Windows,
so skip the test on Windows. cmd.com echo didn's seem to work and
neither did trying to use python, but perhaps it was just me fighting
with the terminal quoting rules :shrug:

related: #16599
related: #16552

Signed-off-by: Christian Brabandt <cb@256bit.org>