New platform foundation on server

[kimjoar]

Tracking the high-level tasks as we prepare for the initial merge of new platform (#9675) into master:

- [ ] Integration test setup

Completed:

• Document the way new platform is integrated into legacy one
• Directory structure
• Choose route/config schema solution
• TypeScript support
• Run old and new platform at the same time
• Ensure log format is identical between new and old logging code
• Plugin system: Plugins must be able to specify config
• ES clients
• Http server
• Expose Native observables instead of RxJS observables (PR)

[epixa]

@azasypkin I added a "remove typescript" bullet and removed the build system bullet from this meta list.

[sorenlouv]

Are we going away from Typescript?

[epixa]

@sqren We're separating this initial new platform work from typescript for the sake of pragmatism. The new platform work is a lot closer to being merged than first-class support in our build system for typescript, so we don't want to block the former on the latter.

See #18780 for tracking the typescript support in the build system.

I'll share this more widely with the team this week since I'm sure other folks will be curious.

[sorenlouv]

Makes sense - good to hear the new platform is progressing.

[azasypkin]

Closing this one as all tasks except for Integration test setup have been completed, but since Integration test setup is meta issue by itself we'll track it in #12699.