Gas benchmarking in 4337 tests outputs gas used for the transaction instead of user operation gas

[mmv08]

Description

Shebin and I were looking at the gas discrepancy between our local bundler tests and the Alchemy bundler:

safe-modules/examples/4337-gas-metering/README.md

Line 15 in 32fc6f5

| **[Without Paymaster](../../modules/4337/test/gas/Gas.spec.ts)** | Yes | 415213 | 447632 | 182081 | 426139 | 160575 | 467926 | 202374 |

We realised that in the 4337 tests, we consider transaction gas instead of the user operation gas [what we use in benchmarks].

We should adjust the 4337 tests to use the same method. Reference code is available here