Fix dynamic conversions

[pokornyd]

Motivation

Fixes #265

Adds missing ToDynamic implementations for IEnumerable<Reference> values and for AssetWithRenditionReference. Fixes incorrect FromDynamic implementations on BaseElement and adds round trip tests element → dynamic → element

Checklist

• Code follows coding conventions held in this repo
• Automated tests have been added
• Tests are passing
• Docs have been updated (if applicable)
• Temporary settings (e.g. variables used during development and testing) have been reverted to defaults

How to test

If manual testing is required, what are the steps?

[codecov]

Codecov Report

Attention: Patch coverage is 73.77049% with 16 lines in your changes missing coverage. Please review.

Project coverage is 84.13%. Comparing base (735db03) to head (39a3f81).
Report is 5 commits behind head on master.

Files with missing lines	Patch %	Lines
...ment/Models/Shared/AssetWithRenditionsReference.cs	68.29%	7 Missing and 6 partials ⚠️
...ent.Ai.Management/Modules/HttpClient/HttpClient.cs	40.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #283      +/-   ##
==========================================
- Coverage   84.48%   84.13%   -0.36%     
==========================================
  Files         288      288              
  Lines        2933     2975      +42     
  Branches      233      242       +9     
==========================================
+ Hits         2478     2503      +25     
- Misses        365      374       +9     
- Partials       90       98       +8     

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