fix compilation and tests on MacOS

Context

Closes #258 (closed)

Major modification

1. add: fmt/stl.h include to DynamicAttribute to support the storage of vectors

⚠️ Since Attributes can be of any type, DynamicAttribute includes might increase drastically if we start to include a new file each time a new object formatting is not supported by current includes. As DynamicAttribute is one of the core objects, it is not desirable and could require a refactor of DynamicAttribute formatting

2. enhance structure: improve DataType by matching every standard type based on some features (nb bytes, is floating point, is signed) instead of a few manually chosen ones
3. fix: enforce the use of C++-14 in aidge_export_aidge CMakeLists file (previous fix that was not repercuted)
4. fix: warnings

• remove unused variable warning in 'Leaky.cpp'
• comment unused function 'getDataType()' not labeled 'override' in 'Operator.hpp' and 'OperatorTensor.hpp'
• remove unused reference to this in lambda functions

5. ❗ temporary fix for a test that should completly be redesigned and optimize 'RandomGraph::gen()' function