Add some Support unit tests, #920

[paulirwin]

• You've read the Contributor Guide and Code of Conduct.
• You've included unit or integration tests for your change, where applicable.
• You've included inline docs for your change, where applicable.
• There's an open issue for the PR that you are making. If you'd like to propose a change, please open an issue to discuss the change or find an existing issue.

Adds some Support unit tests.

Partial #920

Description

This adds unit tests for the Support namespace types listed in #920 that don't need Apache Harmony or other test considerations, including:

• IndexableFieldExtensions
• ByteArrayOutputStream
• CastTo
• ListExtensions
• AssemblyUtils
• DictionaryExtensions

[NightOwl888]

Thanks for the PR. Looks good.