Enhance performance of parsing massive test data files. Fixes #2231.
Enhance performance of parsing massive test data files. Fixes #2231.

This especially affects cases where tests/keywords have a big amout of
keywords directly under them. With a massive file (40 tests, 10k kw/test)
savings were huge and parsing time dropped from ~30min to ~30s. With a
big file (40 tests, 100 kw/test) savings were pretty small (0.5s vs 0.4s)
and with smaller files benefits are even smaller.

jaloren/robotframework,jaloren/robotframework,snyderr/robotframework,robotframework/robotframework,snyderr/robotframework,HelioGuilherme66/robotframework,alexandrul-ci/robotframework,alexandrul-ci/robotframework,alexandrul-ci/robotframework,robotframework/robotframework,HelioGuilherme66/robotframework,alexandrul-ci/robotframework,HelioGuilherme66/robotframework,joongh/robotframework,jaloren/robotframework,joongh/robotframework,snyderr/robotframework,jaloren/robotframework,alexandrul-ci/robotframework,robotframework/robotframework,snyderr/robotframework,snyderr/robotframework,jaloren/robotframework,joongh/robotframework,joongh/robotframework,joongh/robotframework