Move deployment contract logic in Private Kernel Circuit

[jeanmon]

Description

This resolves #684

In common_contract_logic() method, we should create new contract data in public_inputs only when the boolean
public_inputs.constants.tx_context.is_contract_deployment_tx is true.

As a consequence, one unit test is failing due to the expectation that there must be some contract data even though the underlying transaction request does not deploy any contract. This was replaced by an assertion that no new contract data
is present in public_inputs.

Checklist:

• I have reviewed my diff in github, line by line.
• Every change is related to the PR description.
• I have linked this pull request to the issue(s) that it resolves.
• There are no unexpected formatting changes, superfluous debug logs, or commented-out code.
• The branch has been merged or rebased against the head of its merge target.
• I'm happy for the PR to be merged at the reviewer's next convenience.

[dbanks12]

Great work! LGTM.