[Backport] Version bumps from 1.6.0 release (#2965)

This PR backports version bumps from release branch
`release-polkadot-v1.6.0` back to `master` and also moved `prdoc` files
related to the release to the appropriate folder

prdoc/1.6.0/pr_2811.prdoc

@@ -0,0 +1,13 @@
+title: "Interlacing removes the region on which it is performed."
+
+doc:
+  - audience: Runtime User
+    description: |
+      The current implementation of the broker pallet does not remove
+      the region on which the interlacing is performed. This can create
+      a vulnerability, as the original region owner is still allowed to 
+      assign a task to the region even after transferring an interlaced
+      part of it.
+
+crates:
+  - name: "pallet-broker"