Extended printf test with new mixed format cases (#1988)

According to work plan from issue #1058

Added new case `TYPE_MIXED_FORMAT_RANDOM` which focus on three factors:

-data before conversion flags - this is randomly generated ascii string
-randomly generated conversion flags - integer or floating point, for
each flag specific argument is generated
-data after conversion flags - this is randomly generated ascii string

Moreover, due to fact in case of `TYPE_MIXED_FORMAT_RANDOM` test is
generated on the fly, logging of negative result was extended.