Fix std::array support by improving get_back_inserter template resolution, closes #323

[Dobiasd]

• Remove unused Container template parameter from get_back_inserterstd::array specialization
• Remove explicit template parameters from get_back_inserter calls to allow proper template argument deduction
• Fix const qualifier issue in swap_keys_and_values by using OutVal instead of InKey

These changes ensure std::array containers work correctly with all FunctionalPlus functions
that use get_back_inserter, including transform, generate, filter, and other container operations.

Fixes compilation errors with std::array in:

• rotate_left function
• transform operations
• swap_keys_and_values function