Locate inner classes tests in outer test class if JUnit4 is used

[EgorkaKulikov]

Description

JUnit4 does not allow to run tests for both outer and inner class.
To avoid losing coverage, we locate all test methods for inner class in a body of outer test class.

Type of Change

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

How Has This Been Tested?

Regression and integration tests

Standard scenarios to generate and run tests with nested classes for ALL supported test frameworks
Regression checks for classes without nested ones.

Manual Scenario

Check test generation for the following class

public class OuterClass {

    public int sum(int a, int b) {
        return a + b;
    }

    public class InnerClass {
        public int min(int a, int b) {
            if (a > b) return b;
            else return a;
        }
    }

Checklist (remove irrelevant options):

This is the author self-check list

• [+] 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
• New documentation is provided or existed one is altered
• [+] No new warnings
• New tests have been added
• All tests pass locally with my changes