* initial draft refactor of Spanner db guide
* heading and formatting changes
* updated examples per variable linter warning
* post-feedback: intro for service account section, formatting
* fixing var entries for linter
* casing issue for linter
* codex issues - db service account description and typo
* changing grep statement to find token role for service act
* moved images to strapi, + some clarification changes
* moved cloudsql db images to strapi, removed images from github
* review edits for consistency and clarity
* cleaning up the troubleshooting section
* cleaning up the troubleshooting section
* restore troubleshooting include
* updating the query to find service account and role
* post-feedback from Gavin