CNG gitlab-shell: remove excess & Ruby (v2)

What does this MR do?

Refactor the gitlab-shell container:

1. Base on gitlab-base instead of gitlab-ruby
2. Use make install to install binaries
3. Use a staging image to chown/chgrp/chmod in order to reduce layers / size

Impact

image	tag	size (skopeo)	size (docker)
gitlab-shell	main	347,346,674	937,613,647
gitlab-shell	shell-remove-ruby-v2	110,881,835	257,519,898
	DIFF	236,464,839	680,093,749
gitlab-shell	main-ubi8	237,052,066	602,388,185
gitlab-shell	shell-remove-ruby-v2-ubi8	150,051,412	389,372,700
	DIFF	87,000,654	213,015,485

Two sizes are listed:

• Skopeo listed the total compresses layer sizes (storage / transit)
• Docker lists the total uncompressed layer sizes (consumption / usage)

Related issues

Primary:

• Closes gitlab-org/charts/gitlab#2242 (closed)

Secondary:

• gitlab-org/charts/gitlab#3268
• gitlab-org/charts/gitlab#1257 (moved)
• gitlab-org/charts/gitlab#2697 (closed)

Checklist

See Definition of done.

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

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

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Integration tests added to GitLab QA
• The impact any change in container size has should be evaluated