## Summary of the Pull Request
Currently, both when the tab is already closed, and when there is a
request to close a tab (might be rejected), we go through the same flow
in TerminalPage.
This might leave the system in inconsistent state, as the side-effects
of closing will persist even if the closing was aborted.
This PR separates between the two flows, by introducing a CloseRequested
event to the TabBase.
This event is used to inform the upper tier (the terminal page) about
the request and to trigger the same logic that happens when the tab is
closed directly from the terminal page (e.g., by clicking close on the
tab view).
The Closed event will be used only to handle the actual closing of the
tab. It will ensure that the tab gets removed from the terminal page if
required.
As a result, it a read-only pane will be closed non-interactively (aka
connection exits), the tab closed flow will be invoked, and no user
prompt will be shown.
## References
<!-- Please review the items on the PR checklist before submitting-->
## PR Checklist
* [x] Closes https://github.com/microsoft/terminal/issues/9572
* [x] CLA signed. If not, go over [here](https://cla.opensource.microsoft.com/microsoft/Terminal) and sign the CLA
* [ ] Tests added/passed
* [ ] Documentation updated.
* [ ] Schema updated.
* [ ] I've discussed this with core contributors already.
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