0027191: Documentation - redesign of information architecture -- renaming (2)

Move debug and upgrade user guides to corresponding folders on upper level

Related: remove "debug" pattern from .gitignore to avoid ignoring relevant folder in dox

dox/FILES_HTML.txt

@@ -43,8 +43,8 @@ dev_guides/contribution/coding_rules.md
 dev_guides/contribution_workflow/contribution_workflow.md
 dev_guides/git_guide/git_guide.md
 dev_guides/tests/tests.md
-dev_guides/debug/debug.md
-dev_guides/upgrade/upgrade.md
+debug/debug.md
+upgrade/upgrade.md
 dev_guides/visualization/pbr_math.md
 
 dev_guides/building/building.md

dox/FILES_PDF.txt

@@ -25,7 +25,7 @@ dev_guides/documentation/documentation.md
 dev_guides/contribution/coding_rules.md
 dev_guides/git_guide/git_guide.md
 dev_guides/tests/tests.md
-dev_guides/upgrade/upgrade.md
+upgrade/upgrade.md
 dev_guides/visualization/pbr_math.md
 
 tutorial/tutorial.md