Create AnonymousFunctionDescriptor

Will be used to check if the descriptor represents a function literal
Minor refactoring in Function/PropertyCodegen

Check if we need to generate code before calling generateMethod()
There were 4 such checks, 2 of them in PropertyCodegen, one in
FunctionCodegen.gen() and one in ClosureCodegen. Every usage except the last
was prepended with the check
Minor refactoring in FunctionCodegen

Combine two nested classes, MethodBounds and LocalVariablesInfo, into one
MethodInfo. Rename some methods. No logic has changed
Simplify FrameMap construction in FunctionCodegen
Extract generation logic from FunctionCodegen

Create a new class FunctionGenerationStrategy, which is used to specify exactly
how the body of a function will be generated. This is made primarily to factor
out the hard dependency on PSI in FunctionCodegen.generateMethod(). The PSI
element is now optional and is only used for debug information (as an argument
to newMethod() and endVisit()). This also helps to refactor the confusing logic
about generating default property accessors.

Assert for whether we generate code now for the declared member is now useless,
since generateMethod() will be used also for generating any possible members.

Also surround with "if ( != null)" some method call in genJetAnnotations(), as
null is possible here
Refactor copy() function generation for data classes

Use FunctionCodegen and the newly created FunctionGenerationStrategy to
generate the needed instructions. Make some methods in FunctionCodegen private
since they're not used anymore outside of the class
Refactor componentN() function generation

Adopt to the new FunctionGenerationStrategy
Refactor FunctionCodegen.genJetAnnotations()

Always map descriptor to the callable method and take the signature from there,
since this way the signature appears to be more accurate. The whole
"mapSignature vs mapToCallableMethod.getSignature" story needs some
investigation though.

Also make the method non-static, remove useless checks, etc
Get rid of FunctionCodegen.MethodInfo

generateMethodBody() is now responsible for generating the local variable
table, therefore the data class MethodInfo is not needed anymore to return
multiple values from it
Remove useless methods from codegen utils
Remove useless parameter from FunctionGenerationStrategy