[Seven] - `@plone/helpers`

[sneridagh]

Important

If you are not a member of the Volto Team or Developers Team in the Plone GitHub organization, then do not work on or comment on this issue.

The Volto helpers need to be refactored into TypeScript, and moved to @plone/helpers.
Could be that some of them are not relevant for Seven, but let's use common sense for now, we can remove them later.

Move the tests too.

Link to the parent PLIP

#6638