phosphor-pid-control: MissingIsAcceptable patch

This is a partial implementation of the ideas here:
https://github.com/openbmc/phosphor-pid-control/issues/31

Renumbering and reordering the recipe file, to help keep the patches in
sequence: TempToMargin first, MissingIsAcceptable next.

A new configuration item is supported in the PID object, named
"MissingIsAcceptable" (for D-Bus) or "missingIsAcceptable" (for the old
config.json). The value is an array of strings. If these strings match
sensor names, those sensors will be flagged as "missing is acceptable",
that is, they can go missing and the zone will not be thrown into
failsafe mode as a result.

This can be handy for sensors that are not always available on your
particular machine. It is independent of the existing Availability
interface, because the decision to go into failsafe mode or not is a
property of the PID loop, not of the sensor itself.

Tested: It worked for me. Also, added a unit test case.

Patch Tracking Bug: b/269219517
Upstream info / review: https://gerrit.openbmc.org/c/openbmc/phosphor-pid-control/+/60888
Upstream-Status: Submitted
Justification: Awaiting upstream review

Google-Bug-Id: 266217080
Google-Bug-Id: 269219517
Signed-off-by: Josh Lehan <krellan@google.com>
Change-Id: I26bc83001a5398ee9e87427b52fe4f15b7f81de7
(cherry picked from commit bc8ac9a7d523b2cfb17229e16f4add75b2f29595)
Signed-off-by: Josh Lehan <krellan@google.com>