Missing tests added
Use codegen box tests for tail calls as diagnostic tests too
Indirect tests for tail call diagnostics removed
No need to store a list of recursive call expressions in trace
Do not rely on JetCallExpressions in tail-call detection

Calls come in other forms too
TCO: Optimize all function calls, not only JetCallExpressions
TCO: Re-use parameter values already loaded onto the stack for a recursive call
Detecting tail calls through CFA
Properly detect changing 'this' reference in tail calls to members
Unused code removed
Rename class
Got rid of HAS_TAIL_CALL slice