PLR: trigger power lost by timeout

[vovodroid]

Trigger power lost event basing on timeout, rather than on cycle counter. It provides more control and allow to skip false triggering.

Depending on UPS/PSU capacitors, DC/AC bed, it could be 0.1-0.5 second. I put default 10ms, I guess it more or less matches current 3 idle() calls.

To prolong this timeout heaters could be disabled during outage period until power is back.

[vovodroid]

I see that build tests fails with Marlin/src/feature/powerloss.h:216:42: error: 'POWER_LOSS_TIMEOUT' was not declared in this scope

But there is Copying ConfigurationsRepo/config/examples/Prusa/MK3S-BigTreeTech-BTT002/Configuration_adv.h to Marlin/Configuration_adv.h. Obviously POWER_LOSS_TIMEOUT is not not defined there, because it's new define.

[thisiskeithb]

I'll mention it again, but these types of changes should be optional in case the current method works better for someone or a user prefers it.

Disable POWER_LOSS_TIMEOUT in the default config (here) and then conditionally change how PLR is triggered if POWER_LOSS_TIMEOUT is enabled. Then add or modify a test so CI checks include it.

[vovodroid]

Any advantages of current idle() fixed counter over configurable timeout?