[experiment] Remove leaveNode() method on AbstractRector and CallableNodeVisitor

[samsonasik]

It seems the leaveNode seems no longer needed on both AbstractRector and CallableNodeVisitor, also its save nodes to returns and node id to remove properties.

This PR to remove it to both classes.

[samsonasik]

All checks have passed 🎉 @TomasVotruba it is ready for review.

[TomasVotruba]

I've always wanted to remove this mess. Thank you 🙏

Could you test on some old version of a project, where dead-code set removes lot of code? I wonder what performance is before/after.

Some code has to be removed by the dead-code set, so we can see this part being used.

[samsonasik]

I tested in our project with 5617 files with 101 files changed:

Before: 1 minutes 52 seconds

➜  ../rector-src/bin/rector process --clear-cache
                                                                                                                        
 [OK] 101 files have been changed by Rector                                                                             
                                                                                                                        
../rector-src/bin/rector process --clear-cache  1043.92s user 32.09s system 953% cpu 1:52.80 total

After: 1 minutes 50 seconds

➜  ../rector-src/bin/rector process --clear-cache
                                                                                                                        
 [OK] 101 files have been changed by Rector                                                                            
                                                                                                                        
../rector-src/bin/rector process --clear-cache  1037.09s user 32.84s system 968% cpu 1:50.45 total

The different seems not really noticable as only 2 seconds, it just clean up if possible.