refactor(tests): lint decorations_spec, float_spec, multigrid_spec #33274

Problem:
decorations_spec.lua, float_spec.lua, multigrid_spec.lua are not
auto-formatted.

Solution:
Add a special `formatlua2` cmake target, which invokes `stylua` with
an alternative `.stylua2.toml` config.

.stylua2.toml

@@ -0,0 +1,8 @@
+# Alternative settings for special snowflakes like: decorations_spec.lua, multigrid_spec.lua, etc.
+
+column_width = 140
+line_endings = "Unix"
+indent_type = "Spaces"
+indent_width = 2
+quote_style = "AutoPreferSingle"
+call_parentheses = "Input"