JsonPointer: add a .createUnchecked static factory method

Better than try/catch each time we need to create a pointer. And we will need to
create a lot.

Signed-off-by: Francis Galiegue <fgaliegue@gmail.com>
AbstractFullReportTest: also ensure that the context is "popped" correctly

Signed-off-by: Francis Galiegue <fgaliegue@gmail.com>