BSON: Improved exception-related tests and report location of U+0000 in the key-string as part of `out_of_range.409`-message

 Conflicts:
	include/nlohmann/detail/input/binary_reader.hpp
	single_include/nlohmann/json.hpp
	src/unit-bson.cpp

Improve diagnostic messages for binary formats

This commit is the equivalent of #1282 for CBOR, MessagePack, and UBJSON.

BSON: throw `json.exception.out_of_range.409` in case a key to be serialized to BSON contains a U+0000

BSON: throw json.exception.out_of_range.407 in case a value of type `std::uint64_t` is serialized to BSON. Also, added a missing EOF-check to binary_reader.

add constraints for variadic json_ref constructors

Fixes #1292

Improve diagnostic messages

Removed linter warnings

This way, the output_adapter can work on simple output iterators and no longer requires random access iterators.

This is a follow-up to #1210.

Thirdparty benchmark: Fix Clang detection.

CMake 3.0+ refers to macOS’ Clang as AppleClang, which would fail a STREQUAL check. Fixed by changing it to MATCHES.

Fix warning C4127: conditional expression is constant