Retry download_and_extract_gitlab_assets in CI

What does this MR do and why?

This MR makes download_and_extract_gitlab_assets in CI more resilient by retrying it in case it errors.

For the past few months at least, the download has sometimes failed with the following error, which unnecessarily breaks the job if it was just an intermittent infrastructure failure:

$ download_and_extract_gitlab_assets
Downloading from https://gitlab.com/api/v4/projects/278964/packages/generic/assets/production-ee-5c7ec8e431abee39949820dbd3fd49e2fd09a1a0c9fe19b19e066ed390480053/assets-production-ee-5c7ec8e431abee39949820dbd3fd49e2fd09a1a0c9fe19b19e066ed390480053-v2.tar.gz ...
Extracting archive to .
scripts/gitlab_component_helpers.sh: line 414: pop_var_context: head of shell_variables not a function context
gzip: stdin: unexpected end of file
tar: Unexpected EOF in archive
tar: Unexpected EOF in archive
tar: Error is not recoverable: exiting now
scripts/gitlab_component_helpers.sh: line 414: pop_var_context: head of shell_variables not a function context
scripts/utils.sh: line 414: pop_var_context: head of shell_variables not a function context

If you run curl -v https://gitlab.com/api/v4/projects/278964/packages/generic/assets/production-ee-5c7ec8e431abee39949820dbd3fd49e2fd09a1a0c9fe19b19e066ed390480053/assets-production-ee-5c7ec8e431abee39949820dbd3fd49e2fd09a1a0c9fe19b19e066ed390480053-v2.tar.gz right now, you’ll see a HTTP/2 200, so it’s definitely just an intermittent failure.

See as an example: gitlab-org/quality/engineering-productivity/master-broken-incidents#8094 (closed)

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