set up 8.10.3 dev cycle (#416)

Author: pzl

package/endpoint/changelog.yml

@@ -1,3 +1,8 @@
+- version: "8.10.3-preview"
+  changes:
+    - description: TBD
+      type: enhancement
+      link: https://github.com/elastic/endpoint-package/pull/99999
 - version: "8.10.2"
   changes:
     - description: revert transform schema v2

package/endpoint/manifest.yml

@@ -2,7 +2,7 @@ format_version: 1.0.0
 name: endpoint
 title: Elastic Defend
 description: Protect your hosts and cloud workloads with threat prevention, detection, and deep security data visibility.
-version: 8.10.2
+version: 8.10.3-preview
 categories: ["security", "edr_xdr"]
 # The package type. The options for now are [integration, input], more type might be added in the future.
 # The default type is integration and will be set if empty.