Feature: ssv-node version exposed as metric

[eth2353]

Is your feature request related to a problem? Please describe.

We run multiple ssv-node instances. When updating them, we can't easily tell which ones still need to be updated.
We also cannot quickly tell which versions of ssv-node we have deployed.

Describe the solution you'd like
Our preferred solution would be to expose the version via the metrics, similar to how it is done by CL/EL clients. The version could then also be shown in the SSV operator Grafana dashboard.

Some examples:

beacon_teku_version{[...labels...], version="24.1.1"}

lodestar_version{commit="5d93a629c0fd1fdd32160cbf7717e7a6b22f7f2d", [...], version="v1.15.0/5d93a62"}}

nethermind_version{Commit="4f89be99ef7d7cef7f63f4742e4222279c161247", Version="1.26.0-exp.2+4f89be99"}

This keeps it really simple. It seems the convention/best practice is to set this metric's value to 1.

Describe alternatives you've considered

Additional context
Obol's charon client has this exposed via a metric. This was really useful during Lido's last Obol testnet, where all cluster participants pushed their metrics to a central location. It was then possible to see which cluster peers had already updated their charon versions.