[PREVIEW] OGM-605 replace id: { ... } with { ... } in association row representati...

...on for embedded ids

I still need to write more tests, namely:
- composite ids with many to many (bidir)
- composite id @OrderColumn List unidir (i.e. the row keys is not made of a Set)
- alternative AssociationStorageType (i.e. non IN_ENTITY)

But I think it does what OGM-605 expects at least by not having the `games: [ { id.sequenceNo: ... } ]` nor `games: [ { id: { sequenceNo: ... }  } ]`, it now does `games: [ { sequenceNo: ... } ]`

I did not do `playedOn_id` => `playedOn` as that's more a JPA rule than anything else.