Fix error where strings were being tracked on IgnoreCycles (#52253)
* Fix error where strings were being tracked on IgnoreCycles
* Fix comments
Co-authored-by: Eirik Tsarpalis <eirik.tsarpalis@gmail.com>
* Update src/libraries/System.Text.Json/tests/System.Text.Json.Tests/Serialization/ReferenceHandlerTests.IgnoreCycles.cs
Co-authored-by: Eirik Tsarpalis <eirik.tsarpalis@gmail.com>
* Add assertion for IsInternalConverter
* Add tests for types with converter
Co-authored-by: Eirik Tsarpalis <eirik.tsarpalis@gmail.com>