[showtech] Enforce run as root and fix printGpio segfault

[huyc-arista]

Pre-submission checklist

• I've ran the linters locally and fixed lint errors related to the files I modified in this PR. You can install the linters by running pip install -r requirements-dev.txt && pre-commit install
• pre-commit run

Summary

I noticed showtech crash when run as non root due to printGpio segfault.

• Adds error handling to printGpio to prevent segfaults when gpiod_chip_open() fails.
• Enforces root execution for showtech to guarantee complete debug info.
• Update gpio printing format

Test Plan

Ran showtech as non-root

[admin@vpr424 ~]$ showtech --details all
Please run this program as root

Ran showtech --details gpio with invalid gpio path and ensure no crash

[root@vpr424 admin]# showtech --details gpio --config_file "/opt/fboss/share/platform_configs/showtech.json"
I1121 18:42:00.221478  6438 ConfigLib.cpp:50] Using config file: /opt/fboss/share/platform_configs/showtech.json
I1121 18:42:00.221558  6438 Main.cpp:72] Executing: gpio
##### GPIO Information #####
#### GPIO Chip Details /run/devmap/gpiochips/INVALID_GPIO ####
line  0: SCD_DONE        -> Error: failed to read gpio line: GpiodLineTrace: Invalid gpiod_chip* passed in for SCD_DONE
line  1: OVER_TEMP_L     -> Error: failed to read gpio line: GpiodLineTrace: Invalid gpiod_chip* passed in for OVER_TEMP_L
line  2: SYS_PGOOD       -> Error: failed to read gpio line: GpiodLineTrace: Invalid gpiod_chip* passed in for SYS_PGOOD
line  3: P1V2_CP_PGOOD   -> Error: failed to read gpio line: GpiodLineTrace: Invalid gpiod_chip* passed in for P1V2_CP_PGOOD
line  4: SCD_CRC_ERR     -> Error: failed to read gpio line: GpiodLineTrace: Invalid gpiod_chip* passed in for SCD_CRC_ERR
line  5: P1V0_CP_PGOOD   -> Error: failed to read gpio line: GpiodLineTrace: Invalid gpiod_chip* passed in for P1V0_CP_PGOOD
line  6: P1V8_CP_PGOOD   -> Error: failed to read gpio line: GpiodLineTrace: Invalid gpiod_chip* passed in for P1V8_CP_PGOOD
line  7: P3V3_CP_PGOOD   -> Error: failed to read gpio line: GpiodLineTrace: Invalid gpiod_chip* passed in for P3V3_CP_PGOOD
line  8: SCD_PRGM_L      -> Error: failed to read gpio line: GpiodLineTrace: Invalid gpiod_chip* passed in for SCD_PRGM_L
line  9: SCD_HOLD_L      -> Error: failed to read gpio line: GpiodLineTrace: Invalid gpiod_chip* passed in for SCD_HOLD_L
line 12: CPU_QSPI_SEL    -> Error: failed to read gpio line: GpiodLineTrace: Invalid gpiod_chip* passed in for CPU_QSPI_SEL
line 14: SCD_RESET_L     -> Error: failed to read gpio line: GpiodLineTrace: Invalid gpiod_chip* passed in for SCD_RESET_L

[huyc-arista]

@somasun Can we assume showtech can always be run as root user? Non root showtech output is still usefull just not as complete. I don't want this guard to prevent us getting showtech logs if such scenario exist.

[meta-codesync]

@somasun has imported this pull request. If you are a Meta employee, you can view this in D88675606.

[somasun]

@somasun Can we assume showtech can always be run as root user? Non root showtech output is still usefull just not as complete. I don't want this guard to prevent us getting showtech logs if such scenario exist.

I think this should be fine.