Tiny fix for lightmapper DDA

[reduz]

• Ensures only one axis advances at a time
• This fixes extremely corner cases where the DDA may skip over geometry
• As a bonus, clarify to the user that splitting into more meshes may improve the texture size limit.

[jcostello]

Error while building

editor/plugins/lightmap_gi_editor_plugin.cpp:116:6: error: 'LightmapGIEditormPlugin' has not been declared
  116 | void LightmapGIEditormPlugin::_bake() {
      |      ^~~~~~~~~~~~~~~~~~~~~~~
editor/plugins/lightmap_gi_editor_plugin.cpp: In function 'void _bake()':
editor/plugins/lightmap_gi_editor_plugin.cpp:117:9: error: '_bake_select_file' was not declared in this scope
  117 |         _bake_select_file("");
      |         ^~~~~~~~~~~~~~~~~

[jcostello]

Looks they are working much better now. I tried on sponza and in the TPS demo

[clayjohn]

Makes sense. Using lessThanEqual could return multiple channels where the channels are equal. We can't move to lessThan as we could end up with zero channels and then we are stuck.

You just need to remove the old line before this is ready to merge.

[reduz]

This should now be ready

[akien-mga]

Thanks!