Increase default "nesting" level of container type of component directive

Some directives are meant to host formatted content inside, especially things like tabs, dropdowns, etc.

Since the minimum "working" nesting level is `:::` for any component, including simple ones like includes, admonitions, images, etc., it would be very helpful if we could avoid having to revise the entirety of directives as soon as we nest something.

Right now, for example, tabs are:

::::tabgroup
:::tab
OhNoIWantToAddAWarning
:::
::::

Since they'd still work with 1 or 2 extra :::::::::::::::::::::::::::, could we consider slightly increasing the default for some of these containers?

::::::tabgroup
:::::tab
:::warning
NiceThatWasEasy
:::
:::::
::::::

This would be a quite significant life improvement change, especially since we'll keep getting more tabs & all over time