Pin multi-xml gem and cherry-pick GDK fixes into 16.6

What does this MR do and why?

When merging a fix into 16.6, the qa:selectors job failed with:

$ cd qa && bundle install
Fetching gem metadata from https://rubygems.org/.......
multi_xml-0.7.1 requires ruby version >= 3.1.2, which is incompatible with the
current version, 3.0.6

The version got inadvertently bumped from 0.6.0 to 0.7.1. The older version was successfully installed using Ruby 3:

https://gitlab.com/gitlab-org/gitlab/-/jobs/6973687948

Installing coderay 1.1.2
Fetching multi_xml 0.6.0
Fetching unicode-display_width 2.4.2
Fetching zeitwerk 2.6.8
Installing multi_xml 0.6.0
Fetching declarative 0.0.20

Also, it cherry-picks !148912 (merged) to workaround a registry failure because the old image got garbage collected

https://gitlab.com/gitlab-org/gitlab/-/jobs/7174866253

ERROR: failed to solve: registry.gitlab.com/gitlab-org/gitlab-development-kit/asdf-bootstrapped-verify/main:e8a2f3c30d3031c5574957efbaa917bacdeb3f1a: failed to resolve source metadata for registry.gitlab.com/gitlab-org/gitlab-development-kit/asdf-bootstrapped-verify/main:e8a2f3c30d3031c5574957efbaa917bacdeb3f1a: registry.gitlab.com/gitlab-org/gitlab-development-kit/asdf-bootstrapped-verify/main:e8a2f3c30d3031c5574957efbaa917bacdeb3f1a: not found

MR acceptance checklist

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• This MR is backporting a bug fix, documentation update, or spec fix, previously merged in the default branch.
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