Remove const_cast wherever possible

[dkroenke]

Brief feature description:
Check the necessity of all occurring const_casts and remove them if possible.

Detailed information:
To check/improve const correctness in iceoryx we should take a look at all occurring const_casts and refactor them if possible.

[elBoberido]

in some places its just like

int foo() const;
int foo();

where foo calls foo() const
this could probably be fixed by

int foo() const;
int foo();
private:
int foo_impl() const;

then foo() and foo() const can just call foo_impl() const