timestamp gitlab ci job outputs (#13605)

* timestamp gitlab ci job outputs

Based on previous work by @alvicsam in #13047.

* inline timestamp script

Some of our jobs don't check out the substrate repo.

* include .timestamp in pipelines overriding the default before_script

Still not including it in the zombienet jobs, they have their own
timestamping anyway.

* move timestamp.yml to shared pipeline repo

https://gitlab.parity.io/parity/infrastructure/ci_cd/shared