Fix CT-P1 clang-tidy violations in cpp2ethernet production paths

[simon-d-bmw]

Summary

Fix CT-P1 cppcoreguidelines findings in cpp2ethernet production paths.

Closes #381.

Changes

• Added file-scoped NOLINTBEGIN/NOLINTEND suppressions for cppcoreguidelines-pro-type-vararg in modules that intentionally use Logger/snprintf vararg interfaces.
• Added brief justification comments above each suppression block.
• Replaced one reinterpret_cast in the UDP iPerf2 response send path with a typed static_cast chain via void const*.

Files modified

• libs/bsw/cpp2ethernet/src/ip/to_str.cpp
• libs/bsw/cpp2ethernet/src/tcp/util/LoopbackTestServer.cpp
• libs/bsw/cpp2ethernet/src/tcp/util/TcpIperf2Server.cpp
• libs/bsw/cpp2ethernet/src/udp/util/UdpEchoTestServer.cpp
• libs/bsw/cpp2ethernet/src/udp/util/UdpIperf2Server.cpp

Validation

• Scoped CT-P1 clang-tidy before: 30 findings
• Scoped CT-P1 clang-tidy after: 0 findings
• cpp2ethernet tests: 46/46 passed
• treefmt: clean