This reverts commit fd8e49b5bddceaae803670121b603b5eee8c5c08.

* lukas/erts/cpu_time_thread/OTP-15090:
  erts: Make cpu_timestamp use per thread on Linux

* richcarl/eliminate_lib_module/PR-1786/OTP-15072:
  Fix minor issues
  Eliminate call to ct:get_progname() in ts_erl_config
  Use \n escape instead of integer 10
  Move error formatting to erl_error.erl and delete lib.erl
  Move extended parse functions in lib.erl to erl_eval.erl
  Move lib:eval_str/1 into mod_esi.erl
  Remove lib:progname/0
  Eliminate call to lib:progname/1 in slave.erl
  Add ct:get_progname/0
  Remove lib:error_message/2
  Remove lib:flush_receive/0
  Remove lib:send/2 and lib:sendw/2
  Move lib:nonl/1 into yecc.erl

If we don't use per thread the value becomes completely
nonsensical on systems with more than one scheduler.
We keep the old solaris behaviour in order to support the
option, but it only really works when using a single
scheduler.

Introduce is_map_key/2 guard BIF

OTP-15037

This makes the nightly tests slightly more stable as they assert
that the server isn't alive when lcnt:start/0 is called, which it
could still be since the stop command was a plain gen_server call
that didn't wait until the termination was completed.