Bug fixes and refactors from clang-tidy

Summary

• Fix a forward declaration in the wrong namespace in otbRandomForestsMachineLearningModel.h
• Fix a few instances of copy constructor not calling the base class copy constructor
• Fix a virtual near miss in otbTransform (typo in function name overrides the wrong virtual)
• Remove not needed c_str or replace with modern C++

Note: reviewing the four commits individually will be easier because the last one is much larger.

Rationale

Fix bugprone code and potential dangling pointers (#513 (closed)).

Copyright

The copyright owner is CNES and has signed the ORFEO ToolBox Contributor License Agreement.

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Check before merging:

• All discussions are resolved
• At least 2 votes from core developers, no vote.
• The feature branch is (reasonably) up-to-date with the base branch
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• Copyright owner has signed the ORFEO ToolBox Contributor License Agreement