feat(commons): make JSON pretty printing optional via indentOutput

[delatrie]

Context

Currently, all allure-csharp integrations write JSON result files (*-result.json and *-container.json) in a pretty-printed format, i.e., with indentation. While useful for debugging and manual inspection, this creates a substantial overhead to the files' size.

The PR makes the compressed format the default. This results in approximately a 20-30% reduction in the size of JSON files (for our project with Allure NUnit examples, the reduction is 26%).

indentOutput

The PR introduces a new indentOutput configuration property. If set to true, the result files will be pretty-printed, resulting in the original behavior.

Other changes

• fix schema links in Allure.SpecFlow.Tests and Allure.Xunit.Examples
• set indentOutput to true for all test projects
• add a proper cleanup for the tmp directories created during the tests in Allure.Net.Commons.Tests.FileSystemResultsWriterTests
• disable secondary reporter discovery in Allure.Xunit.Examples

Checklist

• Sign Allure CLA
• Provide unit tests