[PE-1788] Use safe_yaml for report parsing - see the original commit message:

[PE-1081] Use safe_yaml for report parsing

This patch changes the report parsing code to use safe_yaml
to prevent security vulnerability. As safe_yaml deserializes
into basic data types only, further changes were needed
to transform the deserialized data into structure expected
by the original code.
[PE-1788] Tests for changes related to the use of safe_yaml - see the original commit message:

[PE-1081] Tests for changes related to the use of safe_yaml

This patch updates spec tests for the changes related to
the use of safe_yaml for report parsing.
While at it all the related test code is modernized.