[opentelemetry-demo] Refactor component env vars to better handle service names

[TylerHelmuth]

Also, I think we should refactor something to make setting env var easier. Adding env vars for specific services that rely on other services (and therefore the Release name) doesn't feel graceful.

I can open an issue for this later.

Originally posted by @TylerHelmuth in https://github.com/open-telemetry/opentelemetry-helm-charts/pull/337#discussion_r953223476

[TylerHelmuth]

/cc @wph95

[dineshg13]

Currently demo application isn't working. See #358 . When i manually fixed that in my environment , am seeing that checkout service is unable to connect to email service

{"message":"failed to send order confirmation to \"[email protected]\": failed POST to email service: Post \"demo-email-service:8080/send_order_confirmation\": unsupported protocol scheme \"demo-email-service\"","severity":"warning","timestamp":"2022-09-09T01:22:19.778637815Z"}

[TylerHelmuth]

@2start would you like to take point on this issue?

[klaudworks]

#363 describes the issue in more detail.