Improve isAccessible checks

[sofurihafe]

Description

Problematic scenario is described in pull#1685.

This PR improved isAccessibleFrom method by adding extra checks for the object on which the call (field accessing) happens in order to be able to deal with such situations.

Refers to # (1677)
Further work of pull#1685

How to test

Automated tests

utbot-samples; mostly AssembleModelGeneratorTests

Manual tests

1. Launch Contest Estimator with the following settings:

timeLimit = 128
methodFilter = "spoon.support.reflect.code.CtAssignmentImpl.getAssigned"
projectFilter = listOf("spoon-core-7.0.0")

2. Verify that the test compiles successfully and that there are necessary reflection usages instead of direct field accesses (see issue no. 1677).