[1.1.x] Blink the value on non-homed axes

[MrsTonedOne]

Description

This kept tripping me up, Blinking a ? on the label suggests that the firmware isn't sure about the axis itself (such as it doesn't know what steppers is which axis), blinking the value more appropriately suggests that it isn't sure about the value.

Benefits

Increasing native/intuitive understanding of status messages

Related Issues

fixes #3737

[thinkyhead]

• Does the '?' / ' ' overwrite all the characters in the value?
  I suspect this will blink between 123 and ?23 or _23.
• This also needs to be implemented for the graphical display.

[Sineos]

Is there any scenario where a non homed axis makes any sense? Otherwise I would vote for a clear text message, e.g. "Axes not homed", "Home first" instead of blinking ? or values.

[MrsTonedOne]

There isn't enough space to state that, and axes can be homed individually so we would need to be able state it per axis. Keeping the value is also important because knowing the delta from the starting position can be helpful, particularly when working on the unit

[thinkyhead]

Rebased, repaired, completed.

• Implemented for graphical display.
• Now overwrites the whole string.
• Simply substitutes '?' for digits.