Fix warnings with `-Wcast-align=strict`

## Brief feature description

When compiling with gcc and `-Wcast-align=strict` there are some warnings in the C binding and in the iceperf example. These should be fixed.

## Detailed information

For the warnings in the C binding @elBoberido proposes to replace
```
/// @brief handle of the chunk header
typedef struct
{
// could be empty but then we get `struct has no members` warning
uint8_t do_not_touch_me[1];
} iox_chunk_header_t;
```
with
```
/// @brief handle of the chunk header
typedef struct iox_chunk_header_opaque_t iox_chunk_header_t;
```

Additionally, see the following comments:
https://github.com/eclipse-iceoryx/iceoryx/pull/1774#discussion_r1015440294
https://github.com/eclipse-iceoryx/iceoryx/pull/1774#discussion_r1015530501

Start by compiling the C binding and the iceperf example with GCC's -Wcast-align=strict, then inspect the warning locations and the two linked discussion comments. Apply the proposed opaque chunk-header approach where appropriate and address the remaining alignment warnings; done means both targets compile without these warnings.

Written by the indexing model from the issue text.