Helm chart should support specifying a different service account

[matthchr]

Describe the current behavior
The Helm chart always uses the default service account

Describe the improvement
We should support a config option allowing the user to bring their own service account

This request was extracted from #2343

[matthchr]

This is a user ask but we're uncertain of the exact use-case. Waiting for more user input before implementing this feature.

[matthchr]

We still think this might be interesting to do but we're not 100% committed to doing it yet. Leaving it open for now as we think about it further.

[matthchr]

No change from above, except now we don't use the default service account we use a custom-named one (so that we can associate it with workload identity). It still is not currently user configurable.

[matthchr]

Closing this as we don't understand the value and there hasn't been much user interest since it was opened.