Saving Discover/Visualize/Dashboard/Graph saved objects allows duplicate titles

[kertal]

Kibana version:
master, other versions have to be tested

Describe the bug:
When you save a new dashboard/saved search/visualize/graph, and choose an already existing name, you'll get a warning, that once you click on save again, the existing saved object will be overwritten. However, this is not the case, there's a new entry with the same name available.

Steps to reproduce:

1. Create a dashboard, save it named 'test'
2. Save it again, selecting "Save as a new dashboard", don't change the name

3. Confirm to overwrite by clicking on 'Save', now you've a duplicate in you dashboard list.

Expected behavior:

Dashboard should we overwritten

[elasticmachine]

Pinging @elastic/kibana-app (Team:KibanaApp)

[timroes]

I wonder if this ever should have worked? I can't remember we ever overwrote saved object "by title" when saving. Do we really want to overwrite here, or rather just prevent saving something with the same title that already exists?

[kertal]

I think the text of this save box was changed, but not the behavior. See 6.8 dashboard save

You're right, it never worked, to have a given duplicate overwritten. And I think it's fine, if a user want's a duplicate, she/he can have a duplicate. So we've just to adjust the message.

[timroes]

The text was changed in #47443 but the behavior stayed the same, so I'd suggest we revert (or find a new good) wording for the dialog.