fixes #87668

This reverts commit 6c9b23ed, reversing
changes made to 085abd5f.

* wip 2

* use viewlet stubs

* fix layering issue

* fix saveState and contextmenus

* move context menu logic into panecomposite

* revert tasks.json

* tasks again

* add showHeaderInTitleWhenSingleView values

* patch tests

* some cleanup

* more cleanup

* start view

* merging conflicts

* fix title and dnd

* adding missing api surface to pane composite

* additional merge resolution

* rename splitview panels to panes

* rename files

* customViewPane

related to #84715

For #81574

This applies the fix from #84878 to a number of other descriptor classes in our codebase

For #81574

See #84669 for details of the problem around strict function types. This change converts `SyncActionDescriptor` to use a static `create` function. This allows us to make the `create` function generic so that it can take the correct types for strictFunctionTypes

https://github.com/microsoft/vscode-codicons/commit/5131e329ebb7d7a0de10e9216da5c492115a41a1