Bytecode verification error after instrumentation of constructors (<init> methods) because of leaking this

[dmitrii-artuhov]

Currently lincheck omits transformation of <init> methods in the transformers chain (see LincheckClassVisitor::visitMethod).
There is a problem with passing object references to injection methods. This may be observed for instrumentation of GETFIELD/PUTFIELD instructions in constructors:

• Injections::beforeReadField function accepts as 1st parameter a reference to the object, on which mentioned instructions are invoked.
• However, if this object is this of the class instance being constructed, then passing it as a parameter to any function will cause VerifyError exception when the jvm will try to load transformed class.