* sverker/erts/robustify-dist-entry-states/OTP-15297:
  erts: Refactor port dist_entry & conn_id into PRTSD
  Remove ugly fail case macros
  Consolidate distribution entry state transitions
  erts: Fix bug in undocumented system_flag(scheduling_statistics)

* Make connection_id part of the distribution handle as {ConnId, DistEntry}
  in order for BIFs to verify correct connection.
* Make distribution handle opaque to net_kernel.
* Remove some unsafe lockless reads of DistEntry.flags
* Change state ERTS_DE_STATE_EXITING to be more of an internal state that
  prevents erts from enqueue, encode or schedule new data to be sent. Otherwise
  it should behave like ERTS_DE_STATE_CONNECTED.

* raimo/receive-TOS-TCLASS/ERIERL-187/OTP-15145:
  Write testcases for recvtos and friends
  Fix term buffer overflow bug
  Fix documentation due to feedback
  Implement socket option recvtos and friends

When a handler process is terminated due to overload, it reads its
configuration from the configuration database, so it can be restarted
with the same configuration after a small delay. This was earlier done
in a different process, which was spawned off from the terminate
function. This caused a race condition, where in some cases, the
configuration was already removed before it could be read.

The reason for spawning off a process, is to avoid a deadlock due to
the call to logger:remove_handler/1.

This commit moves the call to logger:get_handler_config/1 back to the
handler process - to ensure that the data is still there, but keeps
the call to logger:remove_handler/1 in the spawned off process - to
avoid deadlock.

If the report callback function has two arguments, the second argument
is a map with options to limit the size of the log event. To even
allow a better formatting when the event shall be printed on a single
line, the new option single_line is now included in this
argument.

If a filter fails, it is removed by a call to
logger:remove_filter/1,2. If the log event that caused the failure was
issued on the logger process itself, this would earlier cause a
deadlock due to a gen_server:call to self(). This is now prevented.