v4.1.1

• Handle payload lengths less than SL_MIN_PAYLOAD (64) bytes.
• Update packet tracking details just before returning the complete packet to the calling program instead of when the initial data is received.
• Rename SL_MAX_PAYLOAD to SL_RECV_BUFFER_SIZE for clarity.
• sl_ping(): make serverid and site string buffers optional.
• Do not print certificate verification warnings if LIBSLINK_CERT_UNVERIFIED_OK is set.
• Update mbedtls to v3.6.2.