Disable widget dragging/splitting

[msujew]

Motivation

Closes #552

Change description

Removes all contributed commands which programmatically enable users to split editors. Also disables widget dragging so that it's not possible to split editors that way. I believe the dragging functionality hasn't been used anyway?

Reviewer checklist

• PR addresses a single concern.
• The PR has no duplicates (please search among the Pull Requests before creating one)
• PR title and description are properly filled.
• Docs have been added / updated (for bug fixes / features)

[AlbyIanna]

LGTM

[fstasi]

@ubidefeo can you please check if this also fixes
#793
#656
#909

if split is now disabled we can probably close #909

[ubidefeo]

@msujew @AlbyIanna @fstasi
widget dragging is still possible in the sidebar and allows rearranging of icons

[AlbyIanna]

@ubidefeo do we have a separate issue for that? Let's keep the focus of this PR to "prevent editor tabs from splitting". The reason why @msujew also disabled widget dragging, as far as I understood, was to prevent users from moving the sidebar widgets inside the editor and do stuff like this:

[ubidefeo]

LGTM

Ignore the following in favour of another separate issue

@msujew @AlbyIanna @fstasi
widget dragging is still possible in the sidebar and allows rearranging of icons

[per1234]

please check if this also fixes
#793

It does not. I am still able to reproduce #793 using 2.0.0-rc5-snapshot-c430cf0

#656

It does not. I am still able to reproduce #656 using 2.0.0-rc5-snapshot-c430cf0

[kittaakos]

I am getting an error every time I click anywhere in the IDE. The error is thrown in the customized code. this is not bound (undefined):

gh_940.mp4