Debug 8 columns

[bw1129]

This PR adds an additional 4 columns to the blackbox debug variable for a total of 8 useable columns of data (see associated Blackbox Explorer PR betaflight/blackbox-log-viewer#631). This is extremely useful for logging such things as RPM across all 8 motors of an x8 cinelifter for example, which is very useful for troubleshooting a potentially unhealthy motor or ESC before bad things happen (see attached screenshot). There are many other instances where > 4 columns of debug data would be very useful (Eg, to track the movement of all 5 DNs, etc). The PR involves minor changes to blackbox.c and debug.h. The PR also includes a small change to dshot.c to allow logging of erpm data for up to 8 motors.

[blckmn]

AUTOMERGE: (FAIL)

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[SteveCEvans]

If would be great if we could use this either for a single debug mode with eight channels or two of the existing modes. Perhaps have a debug_mode2 to control it? Being able to look at GYRO_SCALED and D_MIN at the same time would be great, for example.

[bw1129]

@SteveCEvans yea, I like that. I think a case could be made for both, but it would require a lot more extensive changes to have 2 separate debugs, which would also require changes to the configurator BB logging tab

[KarateBrot]

This makes sure we don't write to nonexistent debug channels in case DEBUG16_VALUE_COUNT is smaller than the number of max supported motors. Right now it's both set to 8 and in theory this works perfectly. But if someone changes the number of debug channels to 7 for example and flies with 8 motors, the FC would freeze and we wouldn't know where the bug comes from (not without debugging).

[bw1129]

@KarateBrot good catch, thanks

[haslinghuis]

@bw1129 you forgot to fix line 236 :)

[bw1129]

@haslinghuis oops, thanks, done!

[github-actions]

Do you want to test this code? Here you have an automated build:
Assets
WARNING: It may be unstable. Use only for testing! See: https://www.youtube.com/watch?v=I1uN9CN30gw for instructions for unified targets!