Replace busybox with gitlab base

What does this MR do?

Replace busybox with gitlab-base

Use gitlab-base instead of busybox to share
layers with other GitLab images.

Relates: https://gitlab.com/gitlab-org/charts/gitlab/-/issues/3432

Changelog: changed

The proposed implementation treats gitlab-base as a helper image (like kubectl and certificiates), with optional local overrides.

Busybox is currently used as:

• image for the configure container in various subcharts
• and as image for the run-check container of the upgrade-check Job.

Related issues

Relates #3432 (closed)

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion.

Test Plan

1. Deploy the Chart (and override some gitlab-base image tags)

   helm upgrade gitlab ~/repos/gitlab-chart/ \
     --install -n gtlb-base --create-namespace \
     --set gitlab.webservice.init.image.tag=v15.11.0 \
     --set global.gitlabVersion=15.11.2

2. Verify the configure container use gitlab-base

3. Verify all initContainers complete successfully

4. Repeat with --set global.image.tagSuffix=-ubi8

Required

• Merge Request Title and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com
• When ready for review, MR is labeled "~workflow::ready for review" per the Distribution MR workflow

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA
• Equivalent MR/issue for omnibus-gitlab opened
• Validate potential values for new configuration settings. Formats such as integer 10, duration 10s, URI scheme://user:passwd@host:port may require quotation or other special handling when rendered in a template and written to a configuration file.