## Problem
We have several linters that use Node.js, but they are currently set up
differently, both locally and on CI.
## Summary of changes
- Add Node.js to `build-tools` image
- Move `compute/package.json` -> `build-tools/package.json` and add
`redocly` to it `@redocly/cli`
- Unify and merge into one job `lint-openapi-spec` and
`validate-compute-manifest`
## Problem
This is a prerequisite for neondatabase/neon#12575 to keep all things
relevant to `build-tools` image in a single directory
## Summary of changes
- Rename `build_tools/` to `build-tools/`
- Move `build-tools.Dockerfile` to `build-tools/Dockerfile`
