Issue in iox::cxx::optional class

## Required information

**Operating system:**
E.g. Ubuntu 18.04 LTS

**Compiler version:**
E.g. GCC 7.4.0

**Observed result or behaviour:**

I am getting the build error while compiling the above line.
As we are no able to pass "const" as template argument.

invalid conversion from 'const void*' to 'void*' [-fpermissive]
269 | new (static_cast(static_cast(m_data))) T(std::forward(args)...);
| ^~~~~~
| |
| const void*

**Expected result or behaviour:**
Same code we are able to compile using std::optional.

**Conditions where it occurred / Performed steps:**

Start with the iox::cxx::optional implementation around line 269, using the code and build error shown in the issue to reproduce the failure. Compare the const template-argument case with std::optional; done means the reported code compiles without the const void* to void* conversion error.

Written by the indexing model from the issue text.