Restructuring and addition to permissions docs (#3270)

* docs: Create grants topic

* Update grants

* Restructuring of permissions docs

* Fixing links

Co-authored-by: Dan Heath <76443935+Dan-Heath@users.noreply.github.com>

* Update website/content/docs/concepts/security/permissions/index.mdx

* Update website/content/docs/concepts/security/permissions/index.mdx

* Update website/content/docs/concepts/security/permissions/advanced.mdx

* Apply suggestions from code review

Co-authored-by: Dan Heath <76443935+Dan-Heath@users.noreply.github.com>

* Apply suggestions from code review

Co-authored-by: Dan Heath <76443935+Dan-Heath@users.noreply.github.com>

* Apply suggestions from code review

Co-authored-by: Dan Heath <76443935+Dan-Heath@users.noreply.github.com>

* docs: Add redirect for deleted file

---------

Co-authored-by: Dan Heath <76443935+Dan-Heath@users.noreply.github.com>

website/data/docs-nav-data.json

@@ -138,12 +138,12 @@
                 "path": "concepts/security/permissions"
               },
               {
-                "title": "Assignable Permissions",
-                "path": "concepts/security/permissions/assignable-permissions"
+                "title": "Grant Strings",
+                "path": "concepts/security/permissions/grants"
               },
               {
-                "title": "Permission Grant Formats",
-                "path": "concepts/security/permissions/permission-grant-formats"
+                "title": "Advanced Concepts",
+                "path": "concepts/security/permissions/advanced"
               },
               {
                 "title": "Resource Table",