Allow the same type for number_integer_t and number_unsigned_t (#5815)

* Allow the same type for number_integer_t and number_unsigned_t

basic_json did not compile with NumberUnsignedType == NumberIntegerType
because overloads on both types collided. Such a basic_json now stores
every integer as number_integer: the colliding overloads take a
placeholder type, unsigned C++ integers are converted to number_integer_t,
and value_t::number_unsigned maps to number_integer.

Also fixes two problems this configuration would hit: the unsigned
integer parser accepted values that wrap around to negative numbers, and
dump() overflowed when computing the absolute value of the minimum.

A repeated NumberFloatType gets a static_assert.

Refs #2573

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Use json::with_integers_t in the test and the docs

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* ✅ skip patch test on GCC 5 to avoid internal compiler error

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Fix CI: name the unsigned overload type through template parameters

basic_json used number_unsigned_overload_t<basic_json> while the class was
still incomplete. MSVC rejected it as a recursive alias declaration and GCC
4.9, 5 and 7 crashed with an internal compiler error. basic_json now uses
number_unsigned_overload_type<NumberIntegerType, NumberUnsignedType>, which
also makes the GCC 5 workaround in the patch test unnecessary.

Infer reported a null dereference for the number_unsigned case in
from_json, which cannot happen for a basic_json whose number_unsigned_t is
number_integer_t; assert it.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

* Address review: conjunction/negation trait, astyle-friendly alias, docs table order

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

---------

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

include/nlohmann/detail/output/binary_writer.hpp

@@ -221,7 +221,7 @@ class binary_writer
 
             case value_t::number_unsigned:
             {
-                write_cbor_head(0x00, j.m_data.m_value.number_unsigned);
+                write_cbor_head(0x00, conditional_static_cast<std::uint64_t>(j.m_data.m_value.number_unsigned));
                 break;
             }
 
@@ -1601,7 +1601,7 @@ class binary_writer
                 return calc_bson_integer_size(j.m_data.m_value.number_integer);
 
             case value_t::number_unsigned:
-                return calc_bson_unsigned_size(j.m_data.m_value.number_unsigned);
+                return calc_bson_unsigned_size(conditional_static_cast<std::uint64_t>(j.m_data.m_value.number_unsigned));
 
             case value_t::string:
                 return calc_bson_string_size(*j.m_data.m_value.string, j);
@@ -1643,7 +1643,7 @@ class binary_writer
                 return write_bson_integer(name, j.m_data.m_value.number_integer);
 
             case value_t::number_unsigned:
-                return write_bson_unsigned(name, j.m_data.m_value.number_unsigned);
+                return write_bson_unsigned(name, conditional_static_cast<std::uint64_t>(j.m_data.m_value.number_unsigned));
 
             case value_t::string:
                 return write_bson_string(name, *j.m_data.m_value.string);