split off compiler as dev dependencies

[bobzhang]

Relevant issues:
Allowing compiled code delivery
Make bsb able to compile all third-party artifacts into the top-level lib
bs-json: Consider having the compiled JS in the package?
Separated npm package for bucklescript dependencies
Proposal to add bs-stdlib

Some high level issues to solve:

• Should we prebuild stdlib
  It seems so, otherwise *.js files is not in distribution.
  Pre-build-cons:
  We need make sure that .cm[ji] is the same across all platforms,
  more logistics when bump minor version of compiler
  Pre-build-pros
  No need make bsb capable of building stdlib
• How to ensure
  bs-platform-dev is consistent with the version of bs-platform
  It seems that we can add a version field check, and
  bsb always do such check in the beginning

[jordwalke]

For the "Make bsb able to copmpile all third-party artifacts into top level lib", I made a larger issue which includes that and a couple of other things that let us use (Yarn-pnp, and esy) here. Including the link in case it's relevant.

[TheSpyder]

perhaps split the node package into three?

bs-platform
-> bs-compiler (peer-dev on bs-stdlib)
-> bs-stdlib

That way existing workflows aren't impacted, but projects that need to can depend on compiler (dev dep) and stdlib (normal dev) directly (and manage the potential version conflicts themselves).

[bobzhang]

landed in master