Make animation durations consistent with Kirigami values

Summary:
Right now longDuration is 120ms and shortDuration is 24ms. This presents three problems:

• The durations are far too fast, especially shortDuration, which is so fast that it seems like there is no animation at all.
• The durations are not consistent with Kirigami, which uses 150 for short and 250 for long.
• There is no longer value available, as with the one being added to Kirigami in D28143.

Accordingly, this patch makes the short and long values consistent with Kirigami's values,
and adds a new veryLongDuration value to match the one being added to Kirigami in D28143.

Reviewers: Plasma, davidedmundson, mart

Reviewed By: Plasma, mart

Subscribers: kde-frameworks-devel

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D28144