Kovan chainlink l2 deploy (Synthetixio#1124)

* Better way to determine when to skip ext:Messenger syncs

* More advanced skipping of rebuildCache calls in deploy script

* Test deploy on kovan L1

* Test deploy on kovan l2

* Connecting SNX price feed

* Downgraded @eth-optimism/solc

* Addded more synths to test instance

* Avoid auto hardhat compile on local ovm prod tests

* Add no compile flat to prod tests

* Fix CI local ovm prod tests

* Removed kovan test deploy artifacts

* Clean install

* Deployed to kovan L2

* Update to develop

* Use chainlink abi from node_modules

* Cleaner import of chainlink ABI

Author: eternauta1337