[DMN Designer] Download buttons UX (Development task)

Need to update the DMN toolbar download buttons based on the context described in initial issue.

Implementation suggestions can be found in this slide deck. https://docs.google.com/presentation/d/1uq3DZ95LWODhmdL8p9A-xaw8sufe3lBVCWF8E_qVn_g/edit?usp=sharing

Suggestions are as follows:
1. Remove download button that appears as icon dropdown, and leave the Download button that appears spelt out.
2. Make that download button a drop down meny that includes all possible downloading options, separated into two parts - download DMN model and download documentation.
3. Remove download button in the documentation sub tab (that appears on top right of documentation example) to avoid repetition, and just leave the print button there.

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Context:

Today users can:

1) Download the diagram picture by using this component:

2) Download the DMN file by using this component:

3) Print or Download the documentation as PDF by using the Print button (into the Documentation tab):

4) Download the documentation as DOC by using the Download .doc file button (into the Documentation tab):

Problem:

The "Download" concept is getting confusing for users.

As a user, I want to be able to:

• Download the documentation as a .PDF file
• Download the documentation as a .DOC file
• Print the documentation

Notice:

This component can be removed (if UX considers that it's necessary):