allow passing args when using `aztec-postprocess-contracts`

[twt--]

transpile_contract_and_gen_vks.sh currently ignores any provided args. This PR updates the script so that arguments are passed to the bb aztec_process, enabling things like

aztec-postprocess-contracts --input target/mycontract.json

using the aztec-postprocess-contracts helper instead of needing to run bb manually with:

docker run [...] \
  --entrypoint=/path/to/bb \
  aztecprotocol/aztec:3.0.0-devnet.4 \
  aztec_process --input target/mycontract.json