Enabling proto3_optional flag

[MukulGarg15]

This PR fixes the Protobuf compilation issue where protoc fails due to proto3 optional fields not being explicitly allowed.
Error message was : Error compiling protobuf files: protoc failed: orchestrator.proto: This file contains proto3 optional fields, but --experimental_allow_proto3_optional was not set.

Changes Made:

1. Updated the build.rs file to add config.protoc_arg("--experimental_allow_proto3_optional");
2. Ensured that the correct .proto files are compiled without errors.
3. Verified that protoc runs successfully and generates the required Rust files.

Why This Fix?

1. Newer .proto files use optional fields in proto3, which require the --experimental_allow_proto3_optional flag to be set explicitly.
2. Without this fix, developers cloning the repo and trying to build the project would face errors.