Allow multiple strategies to be defined at once for certain destination fields

[ccailly]

Checklist before requesting a review

Please delete options that are not relevant.

• I have read the CONTRIBUTING document.
• I have performed a self-review of my code.
• I have added tests that prove my fix is effective or that my feature works.
• This change requires a documentation update.

Description

Added the possibility of combining several strategies for certain fields in form destinations.
Modification of the UI/UX of the “Associated Items” field:

• More compact interface in the form of a single component
• Removal of the “Add new item” button for an automatic new item system as soon as all previous fields have been completed.

Screenshots (if appropriate):

[AdrienClairembault]

Not sure the word "strategy" should be shown to users, it feels too technical IMO.

[AdrienClairembault]

@orthagh We'll have to take a look at this and see how we can make this config page "simpler" because there are a lot of options right now and it feels overwhelming.