Bazel build for multiple artifacts across languages

[yecol]

Since we have many artifacts in this monorepo, currently the building toolchain for each component is language specific.
It seems bazel is fit for our project, only one building toolchain supports polylang, i.e., cpp/python/Java/Rust, even docker container. Especially for flex-build, maybe it is worth a try.

ref. https://bazel.build/