Single tx safe apps interactions should not use multisend

[rmeissner]

Title/Description

If a safe app triggers only a single transaction, we should not use multisend. This would safe gas and make the decoding easier.

Steps to reproduce

• Use transaction builder
• Add single contract interaction
• Submit

Expected result

• Data of triggered tx to be the contract interaction and to should be contract specified in tx builder

Obtained result

• Data is a invocation of the multisend method with the encoded contract interaction and the to is the multisend