Proposal: have `-config.expand-env` added to the installers

[EStork09]

#1943 talked about this but seems to have gone stale. I can make a PR and add the variable to both the installers as mentioned in the above issue but before I go down that I wanted to double check if this is something that we are avoiding on purpose or if it might just not be a pressing issue.

[splitt3r]

This is a duplicate of https://github.com/grafana/agent/issues/1943 which got closed.

[EStork09]

Sorry @splitt3r, I had the wrong one linked, but the reason it got closed is due to it going stale, not because someone actively closed it.