RFC: Renaming PM APIs

[nashif]

• Rename _sys to sys_
• Rename _sys_soc -> sys_

Fixes #11047

[codecov-io]

Codecov Report

Merging #11972 into master will increase coverage by 0.39%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #11972      +/-   ##
==========================================
+ Coverage   48.07%   48.47%   +0.39%     
==========================================
  Files         281      293      +12     
  Lines       43349    50722    +7373     
  Branches    10392    13038    +2646     
==========================================
+ Hits        20841    24586    +3745     
- Misses      18350    21351    +3001     
- Partials     4158     4785     +627

Impacted Files	Coverage Δ
kernel/idle.c	100% <ø> (ø)	⬆️
subsys/shell/shell_ops.h	41.79% <0%> (-10.85%)	⬇️
drivers/clock_control/nrf5_power_clock.c	50% <0%> (-2.11%)	⬇️
include/net/net_if.h	62.41% <0%> (-0.41%)	⬇️
include/net/net_pkt.h	85.6% <0%> (-0.25%)	⬇️
include/net/websocket.h	100% <0%> (ø)	⬆️
include/device.h	100% <0%> (ø)	⬆️
include/net/socket.h	100% <0%> (ø)	⬆️
include/logging/log_core.h	100% <0%> (ø)	⬆️
subsys/net/lib/http/http_server.c	52.06% <0%> (ø)	⬆️
... and 52 more

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[dbkinder]

doc changes LGTM

[andrewboie]

No objections to this change.
Do we have documentation somewhere which indicates the appropriate use of prefixes (z_, k_, sys_, etc)

[ioannisg]

This seems a safe change to me.

[carlescufi]

@nashif why is this tagged as DNM?

[nashif]

recheck