part of #42116

previously, in the update insight mutation for existing insight series we

1. remove the existing series from the view (this soft-deletes the series)
2. create a new series and attach it to the view (this does a new attach series to view step)
3. update the insight view to be attached to the old series

call 3 was completely redundant as the series was no longer in use. it would just affect 0 rows each time.

now, we check whether the series existed before. if it didn't we just create a new one. otherwise we check what has changed. if it's only presentation metadata we won't trigger an insight recalculation.

Test plan

Added an integration test and manually validated that before/after did not change when creating some insights

see it in action: https://www.loom.com/share/2b893d3691cd40df81a910e60bd42ab5

with sg start enterprise-codeinsights running:

go test -long -run TestUpdateInsight -base-url "https://sourcegraph.test:3443" -v

2022/11/23 17:29:56 Site admin authenticated: gqltest-admin
=== RUN   TestUpdateInsight
--- PASS: TestUpdateInsight (1.37s)
PASS
ok  	github.com/sourcegraph/sourcegraph/dev/gqltest	2.014s