start on new infra/arch docs

[atvaccaro]

Description

Describe your changes and why you're making them. Please include the context, motivation, and relevant dependencies.

Resolves #2672

Creates a couple of high-level architecture diagrams and adds some additional service/environment docs. Should set us up for service/folder-specific READMEs in the next sprint.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation

How has this been tested?

Include commands/logs/screenshots as relevant.

see docs preview

Post-merge follow-ups

Document any actions that must be taken post-merge to deploy or otherwise implement the changes in this PR (for example, running a full refresh of some incremental model in dbt). If these actions will take more than a few hours after the merge or if they will be completed by someone other than the PR author, please create a dedicated follow-up issue and link it here to track resolution.

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• Actions required (specified below)

[github-actions]

Preview url: https://data-infra-2767--cal-itp-previews.netlify.app

[lauriemerrell]

Thanks for doing this, the text all looks good but the data flow diagram is pretty funky now. I think that the old one was doing some stuff vis a vis styling and grouping that you need to account for a bit more.