Suppress warnings in NLOHMANN_JSON_SERIALIZE_ENUM

[nlohmann]

Fixes #3924.

• modernize-type-traits: we use C++11 and don't need to implement our own version of std::is_enum_v here
• modernize-avoid-c-arrays: we don't want to rely on client code to include <array> when using NLOHMANN_JSON_SERIALIZE_ENUM

[coveralls]

coverage: 100.0%. remained the same
when pulling d63ade1 on suppress-clang-tidy-warning-in-macro
into 1c5923e on develop.