Add fileContentsUrl option for CreateYamlFile

[Crustack]

What's changed?

New option fileContentsUrl for the CreateYamlFile recipe to allow file contents from a URL. The fileContents option takes precedence, if both the fileContents and fileContentsUrl has a value.

What's your motivation?

Closes #4011

Anything in particular you'd like reviewers to focus on?

Anyone you would like to review specifically?

Have you considered any alternatives or workarounds?

No

Any additional context

Checklist

• [x] I've added unit tests to cover both positive and negative cases
• [x] I've read and applied the recipe conventions and best practices
• [x] I've used the IntelliJ IDEA auto-formatter on affected files

[timtebeek]

Having some trouble getting the tests to work; will revisit later. To get the same result locally be sure to clear out ~/.rewrite/remote/.