Remove use of submodules

[georgeee]

Explain your changes:

• Remove all submodules and copied-in repositories (except for ocaml-rocksdb, which building strategy makes it non-trivial)

Explain how you tested your changes:

• [x] nix build github:MinaProtocol/mina/georgeee/remove-unnecessary-submodules#devnet to test nix build
• [x] CI passes

Checklist:

• [x] Dependency versions are unchanged
  • Notify Velocity team if dependencies must change in CI
• [ ] Modified the current draft of release notes with details on what is completed or incomplete within this project
• [x] Document code purpose, how to use it
  • Mention expected invariants, implicit constraints
• [x] Tests were added for the new behavior
  • Document test purpose, significance of failures
  • Test names should reflect their purpose
• [x] All tests pass (CI will check this if you didn't)
• [x] Serialized types are in stable-versioned modules
• [x] Does this close issues? None

[georgeee]

!ci-build-me

[georgeee]

!ci-toolchain-me

[georgeee]

!ci-toolchain-me

[georgeee]

!ci-toolchain-me

[georgeee]

!ci-toolchain-me

[georgeee]

!ci-toolchain-me

[georgeee]

!ci-build-me

[georgeee]

!ci-build-me

[georgeee]

!ci-toolchain-me

[georgeee]

!ci-toolchain-me

[georgeee]

!ci-toolchain-me

[georgeee]

!ci-toolchain-me

[georgeee]

!ci-build-me

[georgeee]

!ci-toolchain-me

[georgeee]

!ci-toolchain-me

[georgeee]

!ci-toolchain-me

[georgeee]

!ci-build-me

[georgeee]

!ci-build-me

[georgeee]

!ci-nightly-me

[georgeee]

@mitschabaude and I had a discussion in Slack to discuss pros and cons of this approach.

[georgeee]

A caveat of this approach: each snarky update would require a rebuild of a toolchain. AFAIU snarky is not updated frequently, so this shouldn't be an issue. And check-opam-switch will ensure toolchain is updated on a PR changing this dependency.

[georgeee]

It was decided not to merge this PR at the moment and keep use of submodules between mina-related repositories