Remove protocol buffer compiler

[CGodiksen]

This PR closes #403 by removing the external protoc dependency and replacing it with protox.

[Copilot]

Pull request overview

Removes the external protoc dependency from the build by switching protobuf compilation in modelardb_types to the pure-Rust protox compiler, aligning with issue #403’s goal of eliminating external build tooling.

Changes:

• Replace prost-build’s compile_protos (which requires protoc) with a protox -> FileDescriptorSet -> prost-build flow in crates/modelardb_types/build.rs.
• Remove protoc installation requirements from CI, Docker image build, and user/Python binding documentation.
• Add protox as a workspace dependency and update the lockfile accordingly.

Reviewed changes

Copilot reviewed 7 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
docs/user/README.md	Removes protoc from user build prerequisites.
Dockerfile	Drops protobuf-compiler installation from the image build.
crates/modelardb_types/Cargo.toml	Adds protox as a build-dependency (workspace-managed).
crates/modelardb_types/build.rs	Switches protobuf compilation to protox + prost-build::compile_fds.
crates/modelardb_embedded/bindings/python/setup.py	Removes protoc from Python binding build dependency checks.
Cargo.toml	Adds protox to [workspace.dependencies].
Cargo.lock	Records the new dependency graph introduced by protox.
.github/workflows/build-lint-test-and-upload.yml	Removes protoc setup steps from CI jobs.

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[skejserjensen]

As an additional check, I tried to compile the main branch with protoc installed, the main branch without protoc installed, and this branch without protoc installed on Linux. The main branch compiled correctly with protoc installed, but failed when I uninstalled protoc, while this branch compiled correctly both with and without protoc installed. I also extracted the two Rust files generated from the ProtoBuf files by protoc and protox to check if they contain any major changes. It turns out that either I have made a mistake with deleting the target folder between builds, or the two files are exactly the same.

$ diff modelardb.flight.protocol-protoc.rs modelardb.flight.protocol-protox.rs

$ shasum modelardb.flight.protocol-protoc.rs modelardb.flight.protocol-protox.rs
  b620b3192dbe4ca54cb8ea676997321b71a8f9af  modelardb.flight.protocol-protoc.rs
  b620b3192dbe4ca54cb8ea676997321b71a8f9af  modelardb.flight.protocol-protox.rs