test: use packer 1.11 for the acceptance tests

[jooola]

Apply some changes based on the scaffolding repo: https://github.com/hashicorp/packer-plugin-scaffolding/blob/575ff3773c78b24b19841183214cfb9ed447c095/GNUmakefile

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 33.42%. Comparing base (77bb637) to head (4a1d3a7).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #191 +/- ## ======================================= Coverage 33.42% 33.42% ======================================= Files 11 11 Lines 694 694 ======================================= Hits 232 232 Misses 437 437 Partials 25 25 ```

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