Validate Underscore Entity Property Names

[ceelias]

Ran into an issue with OneLogin integration when it was upgraded to new SDK where one of the Entities had a left over underscore property name: _icon

As it was being tested in the graph project with yarn start command and wasn't uploading any data, it didn't throw any errors. The issue arose when it was tested in dev environment: UPLOAD_ERROR

This issue is to add validation in test tooling and runtime for these property values.

[ndowmon]

Great suggestion @ceelias! I think the validation inside createIntegrationEntity might be a good place for this. https://github.com/JupiterOne/sdk/blob/main/packages/integration-sdk-core/src/data/createIntegrationEntity.ts#L128