build: implement vcpkg Manifest Mode, CMakePresets and update README

[varev-dev]

This PR refactors the project's build system by migrating dependency management from manual vendoring to vcpkg Manifest Mode (vcpkg.json). It also introduces CMakePresets to streamline the configuration process and updates the README.md with a "Development Setup" guide.

The first build will take significantly longer than usual because vcpkg needs to compile deps from source.

Hot to test

# 1. Clean old artifacts
rm -rf build

# 2. Configure project (using the new preset)
# Ensure VCPKG_ROOT is set in your env, or adjust the path in CMakePresets.json
cmake --preset default

# 3. Build
cmake --build build

# 4. Run the agent (verify it starts and loads config)
./build/source/agent/volta_agent

[kox13]

Works great, although workflow file may need changes in the near future, as the checks take too long.