[Refactor]: Update SSV Docker Image Tag (with next SSV mainnet release)

[daverolo]

Refactor Description

Docker image for SSV service must be updated to ssvlabs/ssv-node, starting from version v2.0.0

SSV release of v2.0.0 is expected arround calendar week 43

Version v1.3.8 is the last release that works with the old repo bloxstaking/ssv-node.
This implies that Stereum can only support updates for higher SSV releases if the suggested change is implemented and Stereum has a new release.

To fix this issue we need to change the image to ssvlabs/ssv-node in launcher/src/backend/ethereum-services/SSVNetworkService.js and write playbooks for the Stereum release to adjust existing nodes.

Reason for Refactor

SSV Breaking Change since v2.0.0

Potential Risks

None as long as the next Stereum release includes this change with the next SSV mainnet release.