fix(insights): send proxy service URL to agent

[ebaron]

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Fixes: #413

Description of the change:

• Fixes the value of the INSIGHTS_SVC key in the environment map.

Motivation for the change:

• When Insights integration is enabled, this allows the Agent to send reports to Insights.

[ebaron]

/build_test

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CI build and push: All tests pass ✅ (JDK17) https://github.com/cryostatio/cryostat3/actions/runs/8834790824