Modify proto-to-js.nix to bundle all proto files

[palas]

Changelog

- description: |
    Update `proto-js-bundle` nix output to create bundles for all the `.proto` files
  type:
  - feature
  projects:
  - cardano-rpc

Context

The PR #911 made it easy to generate a JS from the node.proto file, but it was only generating it for that file (node_grpc_web_pb.js). And there are more .proto files in the proto folder. This PR modifies it to generate bundle files for all the .proto files in the proto folder. This PR also uses the opportunity to quote some of the shell variables, so that they work even if they have spaces on them.

How to trust this PR

I tested that it works. I would check that there are no edge cases and that the code style is good.

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• New tests are added if needed and existing tests are updated. See Running tests for more details
• Self-reviewed the diff