Collateral needlessly required

[TotallyNotChase]

Describe the bug

there's a usecase missing from the balancer: it currently makes sure to never use a reserved collateral regardless of whether or not collateral is needed for transaction - which is good
however, if collateral is not explicitly reserved, it still tries to pick its own collateral to reserve and fails with NoSuitableCollateral if that isn't found
that second thing is unnecessary for non script (or similar) transactions and it blocks a pretty valid usecase

To Reproduce
Steps to reproduce the behavior:

1. Create user with empty wallet, say u1
2. Build a transaction, as u1, where u1 consumes a significant amount of ada from u2. Enough ada to cover transaction fees
3. Sign the transaction with u1 and u2
4. Submit

Expected behavior
Tx submits without error