TYPO3 Core

Creating new `ext:reactions` records are broken. And emits a
sql error message. This happens when it's tried to switch to
the core-shipped type.

Using a default value on database level does not work with
all database backends TYPO3 v12 officially supports, which
has been tried with #100088 and mitigated with #100101. So
that's not an option here.

Only option I currently see, is to bake the default value
using TCA default setting, which was the way the original
`type=user dbType=JSON` variant has used when introduced
with #99226 - until it has been shifted with #100088.