Test must only pack if necessary

### Bug Description

Running the test command shouldn't repack the artifact unless it's necessary. Keep a packed file state and use the state service to verify if the file needs to be repacked.

### To Reproduce

Run `snapcraft test` on a project that uses craft testing and see the artifact being packed even if it's not necessary to repack.

### part yaml

```shell
N/A
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### Relevant log output

```shell
N/A
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Start by running `snapcraft test` on a project using craft testing and trace where the artifact is packed and where the state service is checked. Done means the test command preserves the packed-file state and repacks only when the state shows it is necessary.

Written by the indexing model from the issue text.