minibar: add hiffy power control API

[Aaron-Hartwig]

No description provided.

[Aaron-Hartwig]

Some testing astoria

On the minibar:

aaron@astoria ~ $ pfexec humility  hiffy -c Sequencer.sled_powered
humility: attached to 483:3754:004E00243433510737363934 via ST-Link V3
Sequencer.sled_powered() => false

The attached gimlet, unpowered:

aaron@astoria ~ $ pfexec humility probe
[2025-10-10T13:17:05Z WARN  probe_rs::probe::stlink] Target voltage (VAPP) is 0.84 V. Is your target device powered?
[2025-10-10T13:17:05Z WARN  probe_rs::probe::stlink] send_jtag_command 242 failed: JtagNoDeviceConnected
humility probe failed: An error with the usage of the probe occured

I then turn sled power on:

aaron@astoria ~ $ pfexec humility hiffy -c Sequencer.sled_power_enable
humility: attached to 483:3754:004E00243433510737363934 via ST-Link V3
Sequencer.sled_power_enable() => ()
aaron@astoria ~ $ pfexec humility hiffy -c Sequencer.sled_powered
humility: attached to 483:3754:004E00243433510737363934 via ST-Link V3
Sequencer.sled_powered() => true

And on the gimlet we see the probe:

aaron@astoria ~ $ pfexec humility probe
humility: attached to 483:3754:001C002D3433510737363934 via ST-Link V3
humility:        probe => ST-Link V3, VID 0483, PID 3754
humility: probe serial => 001C002D3433510737363934
humility:         core => Cortex-M7
humility: manufacturer => STMicroelectronics
humility:         chip => STM32H7, revision 0x2003
humility:       status => executing, debug halt
humility:  debug units => CSTF(x2) CTI(x2) DWT ETM FPB ITM SCS SWO TMC TPIU
humility:         CSTF => 0x5c004000, 0x5c013000
humility:          CTI => 0x5c011000, 0xe0043000
humility:          DWT => 0xe0001000
humility:          ETM => 0xe0041000
humility:          FPB => 0xe0002000
humility:          ITM => 0xe0000000
humility:          SCS => 0xe000e000
humility:          SWO => 0x5c003000
humility:          TMC => 0x5c014000
humility:         TPIU => 0x5c015000
humility:           R0 => 0x2405d100
humility:           R1 => 0x2405d100
humility:           R2 => 0x0
humility:           R3 => 0x0
humility:           R4 => 0x0
humility:           R5 => 0x0
humility:           R6 => 0x0
humility:           R7 => 0x0
humility:           R8 => 0x0
humility:           R9 => 0x0
humility:          R10 => 0x0
humility:          R11 => 0x0
humility:          R12 => 0x0
humility:           SP => 0x2405d100
humility:           LR => 0x802a8cf
humility:           PC => 0x802a8d2
humility:          PSR => 0x61000000
humility:          MSP => 0x240003b0
humility:          PSP => 0x2405d100
humility:          SPR => 0x7000000