fix: Remove invasive split terminal action

[rschnekenbu]

What it does

Partially removes some intrusive split terminal actions in views

Current situtation:

fix eclipse-theia#12357

Contributed on behalf of STMicroelectronics

How to test

To test in theia:

• Check that by default, split terminal action does not appear on toolbars for various views.
• Check that on terminal views, the split terminal icon is still present when the terminal view is active
• terminal context menu still displays the split terminal entry

Limitations: when a terminal is active, there are still some polluting split terminal entries on some views.

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

[tsmaeder]

I'm still seeing the "Split Terminal" action in the view toolbars. It's disabled, but it's there.

[tsmaeder]

Forget that...after a proper rebuild, it seems to work.

[tsmaeder]

lgtm

[rschnekenbu]

Thanks for the quick review, @tsmaeder! I will create the PR on eclipse-theia repo.

[rschnekenbu]

closed in favor of eclipse-theia#12358