refactor(workbench): display start page without part

[k-genov]

Previously, the primary router outlet was rendered in a workbench part if there were no open views either in the main area or in a layout without a main area. After this change, the primary router outlet is rendered directly without a part, since a part is only a container for views.

closes #492

BREAKING CHANGE: The removal of the workbench part for the start page has introduced a breaking change. Part actions are no longer supported on the start page.

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• [x] The commit message follows our guidelines
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PR Type

What kind of change does this PR introduce?

• [ ] Fix
• [ ] Feature
• [ ] Documentation
• [x] Refactoring (changes that neither fixes a bug nor adds a feature)
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Issue

Issue Number: 492

Does this PR introduce a breaking change?

• [x] Yes
• [ ] No

The removal of the workbench part for the start page has introduced a breaking change. Part actions are no longer supported on the start page.

Other information