chore: Removing Item's Website section & references

- Removed old onboarding slide json and `create_onboarding_docs` methods
- Removed website sections from Item master
- Removed references to item website fields
- Shifted Item doctype website methods to Website Item
- Removed WebsiteGenerator from Item doctype
- Website Items in Homepage Products section
- Removed redundant code from item_group.py
- Fix: Item field filters won’t appear in website

erpnext/hooks.py

@@ -77,7 +77,7 @@ domains = {
 	'Services': 'erpnext.domains.services',
 }
 
-website_generators = ["Item Group", "Item", "BOM", "Sales Partner",
+website_generators = ["Item Group", "Website Item", "BOM", "Sales Partner",
 	"Job Opening", "Student Admission"]
 
 website_context = {