bundle files related to sdk dev tool with generated docs.

bundle files related to sdk dev tool(activity_actions.txt, and etc.) to the
final -docs.zip file since sdk.atree needs to copy these files from
$(OUT_DOCS)/offline-sdk dir.

Test: m -j out/target/common/docs/offline-sdk-timestamp
Bug: b/70351683
Change-Id: I3bfb3c56570dd6728dec272d38c6046e0d44c40f
Merged-In: I3bfb3c56570dd6728dec272d38c6046e0d44c40f