Make toMethodResult function safer

[CaelmBleidd]

Description

Replace in the toMethodResult function unsafe access to soot classes with a safe one (surprisingly called unsafe). If we cannot upload a concrete type from the Runtime, we create an unbounded variable with a type belonging to a field we construct.

Fixes #1670

Type of Change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Regression and integration tests

There are no regression tests since it is quite hard to imitate the problem since it'd require working with a "broken" classpath.

Automated Testing

There are no automatic tests due for the same reason.

Manual Scenario

Run contest estimator reproducing steps from #1670 and check that there are no produced errors.

Checklist:

• The change followed the style guidelines of the UTBot project
• Self-review of the code is passed
• The change contains enough commentaries, particularly in hard-to-understand areas
• No new warnings
• All tests pass locally with my changes