Injector: monitors new Tezos heads on its own

Context

The injector component (e.g. of the smart rollup node) now monitors the new Tezos blocks in the L1 chain on its own. This means that the rollup node does not need to notify the injector of blocks manually. It will allow the injector to have a more accurate (time wise) knowledge of the L1 chain. In particular it will allow the injector to know precisely the protocol with which it should perform the next simulation/injection.

Depends on !7681 (merged). Next MR: !7687 (merged).

Manually testing the MR

CI (refactoring).