support a configurable host reboot count

[geissonator]

The amount of times the host is rebooted is a config option (boot-count-max-allowed in https://github.com/openbmc/phosphor-state-manager/blob/master/meson_options.txt#L69)

A new Redfish schema now allows this value to be updated via Redfish. We should move this value over to a setting so that bmcweb has easier access to it (vs. hard coding 3) and will be able to configure it.

See https://gerrit.openbmc-project.xyz/c/openbmc/bmcweb/+/32513

[geissonator]

@NodeMan97 is working on this one.

[NodeMan97]

https://gerrit.openbmc.org/c/openbmc/bmcweb/+/53745
Waiting to finish CR in order to be merged.