implement contract events (#2161)

* implement contract events

* update runtime

* renaming

* update test code hash

* improve complexity details

* add deposit event base cost

* add test

* Revert "add deposit event base cost"

This reverts commit 58ec010c.

* update test

* Revert "update test"

This reverts commit 6fe61a59.

* Revert "Revert "add deposit event base cost""

This reverts commit 145e8a9b.

* Fix format a bit