Robustify OTel Arrow decoding

[lquerel]

Validation test improvements:

• This PR introduces a layer between encoding and decoding layers to mess up with OTel Arrow records. The goal is to make the decoding layer more robust to invalid streams even if individually each Arrow record is technically well-formed.
• The decoding layer should not panic even if the incoming data are invalid (purposely or not). In such situation, the decoding layer should return an error that the collector need to handle.

Bugs fixed:

• Logs with an empty body are now correctly handled.