consider supporting `vendored` feature to avoid prost dependency during build

[nyurik]

requiring every dependent project to add sudo apt-get install -y protobuf-compiler to all of their workflows is a bit annoying, especially for the .protoc file that has not changed in many years. Would it be possible to use a vendored .rs file, and to have an extra feature that would force build that file? This way most users by default would use the included generated file, but your CI would trigger an error if you update prost crate which would generate a slightly different auto-genned file, which would make the git status show modified file?

Running something like this after cargo build --feature compile-protoc would trigger an error (I have this code as a recipe in most of my justfiles)

if [ -n "$(git status --untracked-files --porcelain)" ]; then
  >&2 echo "ERROR: git repo is no longer clean. Make sure compilation and tests artifacts are in the .gitignore, and no repo files are modified."
  >&2 echo "######### git status ##########"
  git status
  git --no-pager diff
  exit 1
fi

[codeart1st]

Thank you for your suggestion. I'll probably look into it next weekend.