test nightly-distroless

[oioki]

Important changes:

• replace honcho package with native python subprocess calls
• created pythonic granian_entrypoint.py, an equivalent of granian_entrypoint.sh in production
• updated the devsercices healthcheck: bash+curl -> native python call

Small stuff only for testing without merging first:

• devservices: set the image to image: ghcr.io/getsentry/snuba:nightly-distroless for testing locally
• .github/workflows changes are only for testing, can be ignored