[Closed in favour of !2738 consolidation] Reopened-and-updated !2727, Saver-swap EnableOrderBooks checks

[Closed: This piecemeal MR not having been re-merged, going straight to a later stage of function consolidation in !2738 (closed).]

[V106-specific]

This reopens the unwound !2727 (merged).

[Update: I realised I had overlooked the handler_withdraw swap,
and have now added it to this MR for the handler_add_liquidity swap.)

This is alternatively closed by !2738 (closed)
'Early-on (RUNE only) affiliate fees'
, which incorporates it.