[DISCO-3249] Add IconProcessor utility

[gruberb]

References

JIRA: DISCO-3249

Description

PR Review Checklist

Put an x in the boxes that apply

• This PR conforms to the Contribution Guidelines
• The PR title starts with the JIRA issue reference, format example [DISCO-####], and has the same title (if applicable)
• [load test: (abort|skip|warn)] keywords are applied to the last commit message (if applicable)
• Documentation has been updated (if applicable)
• Functional and performance test coverage has been expanded and maintained (if applicable)

[ncloudioj]

Just a few more comments, we're almost there.

A few more notes for future iterations:

• Would this prevent us from running merino/adm locally? Looks like we can use original_url as fallback when exception occurs, so maybe we're good.
• We need metrics to understand how things perform in the wild.
• As I pointed out the HTTP connection pool, I realized that we could download images concurrently if necessary. Again, metrics will lead us to the better solution.

[gruberb]

We need metrics to understand how things perform in the wild.

I will follow up with metrics in a separate PR.

[ncloudioj]

Looks good, thanks! r+wc.

Please add [load test: abort] to the commit message.