CCIP-1903 : offchain compatibility tests

[AnieeG]

Motivation

Offchain Version compatibility validation

Solution

Enables offchain version compatibility test github workflow.
The workflow works in following steps -

1. Fetches the last release in the repo.
2. Fetches the test image related to last release and deploys ccip environment with the test image pertaining to last release. It ensures that contracts and offchain nodes are deployed with last release version.
3. It then upgrades few of the nodes with current commit sha, keeping rest of the node with last release version.
4. With this mixed version node it runs a short duration load test to ensure that
   - off chain version is always compatible with contracts deployed in previous release
   - a DON having nodes with two different versions are working as expected.