Add built-in support for setting OTEL service.version

[BSick7]

When using OpenTelemetry, developers usually want to set an env var like this:

OTEL_RESOURCE_ATTRIBUTES: "service.namespace={{ NULLSTONE_STACK }},deployment.environment={{ NULLSTONE_ENV }},service.version={{ NULLSTONE_VERSION }}"

In Kubernetes, you can do service.version=$(NULLSTONE_VERSION) to ensure that new deployments get the correct value in OpenTelemetry.
However, if not using env var expansion $(...) or on other platforms, this value will only be the correct value if initiated through Terraform.

We should update the deployers to gracefully set service.version appropriately.
It would also be helpful to add service.commit.sha.