Double-click a tab to rename it (#6628)

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## Summary of the Pull Request

When the user double clicks on a tab, show the tab rename box
as if they right clicked on the tab and clicked on "Rename".

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## References

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## PR Checklist
* [x] Closes #6600
* [x] CLA signed. If not, go over [here](https://cla.opensource.microsoft.com/microsoft/Terminal) and sign the CLA
* [ ] Tests added/passed
* [ ] Documentation updated. If checked, please file a pull request on [our docs repo](https://github.com/MicrosoftDocs/terminal) and link it here: #xxx
* [ ] Schema updated.
* [ ] I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different grand plan. Issue number where discussion took place: #xxx

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## Detailed Description of the Pull Request / Additional comments

I added a handler for the `DoubleTapped` event on the tab view item
when we are constructing it for the tab (in `Tab::_MakeTabViewItem`).

The code for that handler was copied the "rename tab menu item" click
handler.

I did not extract the code into a member function because it is very
short (only 2 lines of code) and only used twice so it is not worth
it IMO.

<!-- Describe how you validated the behavior. Add automated tests wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed

src/cascadia/TerminalApp/Tab.cpp

@@ -45,6 +45,15 @@ namespace winrt::TerminalApp::implementation
     void Tab::_MakeTabViewItem()
     {
         _tabViewItem = ::winrt::MUX::Controls::TabViewItem{};
+
+        _tabViewItem.DoubleTapped([weakThis = get_weak()](auto&& /*s*/, auto&& /*e*/) {
+            if (auto tab{ weakThis.get() })
+            {
+                tab->_inRename = true;
+                tab->_UpdateTabHeader();
+            }
+        });
+
         _UpdateTitle();
     }