[sitecore-jss-angular] Fix Editing Scripts component rendered twice in pages

[yavorsk]

• This PR follows the Contribution Guide
• Changelog updated
• Upgrade guide entry added

Description / Motivation

This PR fixes issue where editing scripts are rendered twice (for server and client) in pages edit mode metadata - by rendering the scripts only on the server.

Testing Details

• Unit Test Added
• Manual Test/Other (Please elaborate) - setup local app as rendering host for pages, and make sure client editing scripts are rendered only once in the markup and there is no 'duplicate modules' error in the browser console

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

[stasmaxymov]

@yavorsk Is there a way to run Angular in full SPA mode, without server-side rendering? If yes, the fix might not work with it

[yavorsk]

hey @stasmaxymov , yea I was also thinking about this. In editing mode we always have SSR and since we are rendering these scripts for editing mode only anyway I guess it should be fine

[art-alexeyenko]

This looks good, thank you Yavor.
One thing I'd change is having to set a spy in each test - I'll adjust this in a moment.