Switch build system to earthly

[ellenhp]

This also paves the way for further productionization because the init containers do a lot of the heavy lifting, extracted data is persisted (the whole postgres dump isn't imported into nominatim on each start anymore), serving containers start faster, and a bunch of other cool things.

Hope you like churn because pretty much everything got renamed.

Still to do:

• Update docs
• Update readme
• Copy the list of cities we support to a file somewhere to replace make list
• Verify transit still works (it probably doesn't realistically speaking)
• Get transit working (if it doesn't still work)

And it would be good to have a test plan to avoid more regressions.

Test plan:

• Check base-map functionality
• Check search auto-complete
• Check clicking on search results
• Check car routing
• Check bike routing
• Check walking routing
• Check transit routing

[ellenhp]

Looks like Earthly doesn't handle copy-on-write which is a bummer because that means it'll keep several copies of planet.osm.pbf around, and worse still several copies of the nominatim and photon indices. :/

See: earthly/earthly#2097

[ellenhp]

To close the loop on the multiple-copies issue, this is a problem but ZFS with duplication makes it a non-issue. VDO would probably do the same. It's also only really an issue with planet-scale builds from what I've seen.

[ellenhp]

I'm going to merge this but feel free to comment here with ways we could improve the new build system.