test: add -json flag #4780
Description
For large-scale analysis of unit test results, getting the output in machine parsable formats such as json can be useful. In golang, this can be done by passing the -json flag to go test.
Tinygo currently does not support this feature, although it would be beneficial; we should add it.
Intuitively I think the easiest way to integrate this is using the test2json internal package used in biggo.