Deprecated and Removed for 2020.07

• Device driver-side support for NETOPT_IPV6_IID
• gcoap_finish() and all related options
  • CONFIG_GCOAP_OBS_OPTIONS_BUF
  • CONFIG_GCOAP_REQ_OPTIONS_BUF
  • CONFIG_GCOAP_RESP_OPTIONS_BUF
• gnrc_nettest module (see PR #14306)
• NETOPT_LINK_CONNECTED
• emb6 package