fix(acceptance/snapshots): use s3mock instead of localstack

[pree]

Description

With the deprecation of opensource localstack it's now requiring a license key to run.
A new (one day old) alternative would be MiniStack which is MIT licensed, or alternatively S3Mock from Adobe, which is Apache-2.0 licensed.

In this PR I'm changing it over to MiniStack S3Mock, but I'm still open for discussions which way we want to continue.

Checklist

• This PR contains a description of the changes I'm making
• I read the CONTRIBUTING.md guide
• I updated the version in Chart.yaml if feasible according to Semantic versioning
• I updated the changelog with an artifacthub.io/changes annotation in Chart.yaml
• I update the changelog in CHANGELOG.md
• I updated applicable README.md files using helm-docs
• By contributing this change, I certify I have signed-off on the
  DCO ownership statement
  and this change did not use post-BUSL-licensed code from HashiCorp.
  Existing MPL-licensed code is still allowed, subject to attribution.
  Code authored by yourself and submitted to HashiCorp for inclusion is
  also allowed.

[pree]

Ministack still failing inside the acceptance-<rnd> pod with:

WARNING: Retrying failed request: /bao_2026-03-25-2119.snapshot ([SSL] record layer failure (_ssl.c:1010))
WARNING: Waiting 3 sec...
WARNING: Retrying failed request: /bao_2026-03-25-2119.snapshot ([SSL] record layer failure (_ssl.c:1010))
WARNING: Waiting 6 sec...
WARNING: Retrying failed request: /bao_2026-03-25-2119.snapshot ([SSL] record layer failure (_ssl.c:1010))
WARNING: Waiting 9 sec...
WARNING: Retrying failed request: /bao_2026-03-25-2119.snapshot ([SSL] record layer failure (_ssl.c:1010))
WARNING: Waiting 12 sec...

This is due https on an http listener.

[pree]

@openbao/openbao-k8s-committers waiting on your input before merging this

[eyenx]

LGTM. feel free to merge