Add vcpkg port features

[abeltrano]

Type

• Bug fix
• Feature addition
• Feature update
• Documentation
• Build Infrastructure

Side Effects

• Breaking change
• Non-functional change

Goals

• Allow consumers to choose which project features to build.

Technical Details

• Introduce vcpkg features protocol, server, tests, and tools, with protocol being the sole default feature.
• Rename existing CMake test exclusion variable to match the vcpkg feature option variable names.

Test Results

• Built the project with default features for arm64 (with EC ABI) and amd64 both locally and in the Windows build system and verified they are end-to-end successful, including the link stage which was previously broken for arm64.

Reviewer Focus

• Consider how this might impact the developer inner loop, if at all.

Future Work

• Enable use of SSL in gRPC transport #95

Checklist

• Build target all compiles cleanly.
• clang-format and clang-tidy deltas produced no new output.
• Newly added functions include doxygen-style comment block.