New build script and CI

[farmaazon]

Bazel-managed build

• Use Aspect build https://www.aspect.build/ for CI
• Use bazel in place of sbt in rust buildscript.
• Use remote cache to obtain already built artifacts.
• Research rewriting parts of release workflow from Rust to bazel (without bazel build for the engine)
• Get rid of environment variables replacement infrastructure in Bazel
• Build and run rust build tool using Bazel to avoid unnecessary recompilations of the build tool

CI workflow

• Research how bazel may help in GH actions generation.

Release workflow

• New way of gathering changelog - from PR descriptions?
• Automated fixes branch

Improvements

[farmaazon]

The current release process:

• Test Tuesday's nightly. If it's in an acceptable shape:
  1. Cut off the release branch
  2. Update changelog section on develop
  3. Cherry-pick any needed fixes to release branch
  4. Make release candidate, by running GH release action, and test it. If not ok, go to point iii.
  5. Make the final release. Fix its changelog if needed.
• otherwise, wait for another nightly with necessary fixes.

We may then discuss what needs to be automated (and how)