[DOCS] - Update rules import API sample return

[yctercero]

Description

Super minor update to the rules import API - the returned data now includes another field rules_count which is the total number of rules we calculated a user attempted to import. We used to rely on the errors array + success count to tally this, but that is no longer reliable as the errors can include errors around actions imports (with the rule itself still importing, just without the action if action failure occurs).

Notes

• PR [Security Solution][Rule/Exceptions Import] - Update import toast logic kibana#131873