Use a static SQL dump to seed the ffs_postgres database

[joshleecreates]

Changes

As discussed with @puckpuck — this change seeds the ffs_postgres database using a SQL dump file and an init script. This simplifies setup for the featureflagservice as no Ecto migrations need to be run. One drawback of this change is that it changes the ffs_postgres from using an off-the-shelf image to using a built image. A bonus advantage is that the featureflagservice starts up a bit faster.

Merge Requirements

For new features contributions please make sure you have completed the following
essential items:

• CHANGELOG.md updated to document new feature additions
• Appropriate documentation updates in the docs
• Appropriate Helm chart updates in the helm-charts

Maintainers will not merge until the above have been completed. If you're unsure
which docs need to be changed ping the
@open-telemetry/demo-approvers.

[puckpuck]

#1319 covers all of this and cleans up the protobuf to remove unnecessary items.

[joshleecreates]

Cool 😎