As adding groups needs the TabContainer to be in a valid state,
especially state related to available width, we need to ensure
that the TabContainer is updated before we add groups to it.
<!-- Add brave-browser issue below that this PR will resolve -->
Resolves https://github.com/brave/brave-browser/issues/46615
TEST=VerticalTabStripWithScrollableTabBrowserTest.ToggleWithGroups
### MANUAL TEST:
#### Steps to verify
* Turn on brave://flags/#scrollable-tabstrip feature flag
* Create a tab group
* Toggle tabs orientation to vertical and then back to horizontal
#### Expected behavior
There should be no crash
Sangwoo Ko
fd9e296077