Fix bed leveling issues

[ellensp]

Description

Two bugs

1. a while loop in line_to_destination_cartesian can loop forever.
   Code has while (cnt) but variable cnt is a structure with a X and a Y component. This while does not end.
   Replaced with `while (cnt.x || cnt.y) now addressed by 🐛 Fix bool evalution of XYval and similar types #26936

2. After ba08dcf
   MESH_BED_LEVELING with SEGMENT_LEVELED_MOVES disabled fails to build.
   Updated variable types to be unsigned.

Requirements

Bed leveling (UBL or MESH) with SEGMENT_LEVELED_MOVES disabled

Benefits

Works as expected

Related Issues

[BUG] G26 with SEGMENT_LEVELED_MOVES disabled with UBL has out of bound moves. #26816

[BUG] IS_CARTHESIAN && DISABLED(SEGMENT_LEVELED_MOVES) wont compile error: conversion from 'XYval<unsigned char>' to non-scalar type 'XYval<signed char>' requested #26718

[classicrocker883]

i have a question, for cartesian beds, is it better to have SEGMENT_LEVELED_MOVES? and what would the advantages/disadvantages be for being defined or undefined?

[ellensp]

closing as sjasonsmith found a better fix. #26936
That fixes the bool operation in XYval, vs just avoiding the broken bool

[thisiskeithb]

closing as sjasonsmith found a better fix. #26936
That fixes the bool operation in XYval, vs just avoiding the broken bool

What about the MBL bug?

[ellensp]

oh darn, its a two parter... part 1 is addressed by #26936
But part 2... updated PR to just address this