[vscode] Support property SourceControlInputBox#visible

[planger]

Feature Description:

Support specifying whether an SourceControlInputBox is visible.

[planger]

Related to #5458

[JonasHelming]

we will have a look at this

[KevinK-9]

The UI of the InputBox is provided by the extension, so the API only needs to save and transmit the variables, correct?
Is there an extension to test this with, to see how the visibility variable is used by such an extension or another way to test the implementation?

[msujew]

The UI of the InputBox is provided by the extension, so the API only needs to save and transmit the variables, correct?

@KevinK-9 Yes, that's correct. I believe that's the way it also works for the already existing parts of this API, such as the placeholder.

Is there an extension to test this with, to see how the visibility variable is used by such an extension or another way to test the implementation?

Contributors of such features usually provide a small example vscode extension to test the changes if it isn't already covered by the existing vscode-sample repo. See for a more elaborate example this PR.