fix: Fix Test Monitor examples

[rbell517]

• This contribution adheres to CONTRIBUTING.md.

What does this Pull Request accomplish?

• Remove json extra fields from steps example
• Fix Result model to expect null values inside lists and dictionaries

Why should this Pull Request be merged?

The steps and results examples currently fail when run against main test.

• The result example fails due to some results returning null entries in some lists. This is an exceptional case, but it is the way the API behaves so the client should respect that.
• The steps example is failing because of how the serialization is handled for the example JSON value it uses. That JSON case was never an important case to support so I am just removing it from the example. Strings as values are the only supported value.

What testing has been done?

Examples are now passing when run against main-test