Deprecated and Removed for 2020.07

• Device driver-side support for NETOPT_IPV6_IID (see PR #14354) (merged)
• gcoap_finish() and all related options (see #14550) (merged)
  • Options are not used by gcoap_finish() but by other functions, so state unclear:
    • CONFIG_GCOAP_OBS_OPTIONS_BUF
    • CONFIG_GCOAP_REQ_OPTIONS_BUF
    • CONFIG_GCOAP_RESP_OPTIONS_BUF
• gnrc_nettest module (see PR #14306) (merged)
• NETOPT_LINK_CONNECTED (see PR #14493) (merged)
• emb6 package (see PR #14494) (merged)