[ENHANCEMENT] Add option when adjusting z-offset for build sheets to adjust all build sheets by a relative value

[rcmaniac25]

Adaptation of https://github.com/prusa3d/Prusa-Firmware/issues/2905 for Buddy Board-based firmware.

Enter what type of printer or upgrade the enhancement applies to. Printer type - Mini/Mini+

Is your suggested improvement related to an existing problem? Please describe. No, it's a general time saving feature (see description below)

Describe the expected functionality If you have a single build sheet, the option to switch build sheets does not exist. If I change a nozzle or do some repair/maintenance on the extruder, there's a (good) chance I need to adjust the z-offset for the bed. This is generally easy.

Once you add additional build sheets, the option to switch sheets appears, and now when the same nozzle change/repair/maintenance occurs, each bed will probably need the z-offset adjusted. As a enhancement, allow adjusting all build sheets by a relative amount when adjusting z-offset. This should only show if there's more then one build sheet recorded.

Example:

• Smooth1: -0.543
• Smooth2: -1.122

I set to smooth1 and specify I want to adjust z-offset. I eventually get the following: Do you want to use the current value? Current: -0.543. Default: 0.000 Click NO to use the default value (recommended) [YES] [NO]

If YES is chosen, I would want the following: Do you want to update all sheets? Click YES to adjust all sheets by the same difference between old and new value. Click NO to only adjust this sheet. [YES] [NO]

If NO is chosen and the value resets to default, it should only effect the existing sheet.

If I choose YES for updating all sheets, then all sheets are adjusted by the relative change that occurred to Smooth1. So if I adjusted Smooth1 from -0.543 to -0.600, a difference of -0.057, then Smooth2 would also be adjusted from -1.122 to -1.179 (or I think it would actually save to -1.180 as precision is 0.002-0.003).

The purpose is to save time in adjusting build sheets when a system change occurs. It won't always be perfect, but it means you do a little bit of live-z adjusting instead of digging into a bed, loosing a first layer, or going "oh no, I forgot to adjust it" and needing to stop a print and adjust the z-offset on it's own.

Speaking of live z, it may be useful to have an additional option to live z adjust all sheets, but I don't think it's needed (and could add confusion if you're rushing to quickly adjust the first layer that you realized isn't as perfect as you hoped)