tools/generate-bedrock-data-from-packets: generate less noise for items

if we have only a name (the majority case), we can just return the name directly instead of an object.
this massively reduces the amount of noise in the files as seen in pmmp/BedrockData@f814036229

tests/phpstan/configs/phpstan-bugs.neon

@@ -168,6 +168,12 @@ parameters:
 			count: 1
 			path: ../../../src/crafting/ShapedRecipe.php
 
+		-
+			message: '#^Offset ''name'' on \*NEVER\* in isset\(\) always exists and is not nullable\.$#'
+			identifier: isset.offset
+			count: 1
+			path: ../../../src/crafting/json/ItemStackData.php
+
 		-
 			message: '#^Property pocketmine\\crash\\CrashDumpData\:\:\$parameters \(list\<string\>\) does not accept array\.$#'
 			identifier: assign.propertyType