Fixes #26153: Add a user interface for managing method/block loops in the techniques editor

[RaphaelGauthier]

https://issues.rudder.io/issues/26153

⚠️ work in progress

[RaphaelGauthier]

Here's what it looks like at the moment :

If no foreach has been declared: the ‘Foreach’ tab contains a greyed-out counter :

If a foreach has been declared, this badge is highlighted to show this information, and a banner above the method is displayed with the name of the foreach and the number of iterations so that this information is always visible, even when the method is collapsed:

To declare a ‘foreach’, user must enter the name and keys of this iterator, then validate to activate the feature :

Once the foreach has been declared, the user can modify the name and keys, and add new items on which to iterate.
⚠️ For the moment, this interface isn't finished, so here's a look at how it looks now, compared with the result we're aiming for :

Here is the list of things to finish:

• enable iterator editing (name, keys and items)
• do the same for Blocks
• add a copy-to-clipboard on the banner
• decode, store and encode the foreach list correctly
• add a warning before deleting the foreach