block.dispose(/*healStack*/ true) should not attempt to heal shadow block connections

[kushal4]

Problem statement

Go to https://blockly-demo.appspot.com/static/demos/code/index.html.
Then bring the setter block

Expected Behavior

The setter block shouldnt have the shadow block attached after the math block is delete

Actual Behavior

the setter block contains shadow block after math block is deleted

Steps to Reproduce

1. Go to https://blockly-demo.appspot.com/static/demos/code/index.html.
   2.Create a variable.
   3.Bring the setter variable block to the workspace.
   4.Connect a math block to the setter block containing shadow block.
   5.Delete this math block.

Operating System and Browser

Chrome Desktop

Additional Information

[AnmAtAnm]

Confirmed.

[AnmAtAnm]

This is not specific to the variable set block. This looks like an over application of the healStack argument of Block.prototype.dispose(). It should definitely not be applied to shadow blocks

However, given that it is "heal stack", I'm not convinced it should be applied to value inputs at all. Do we want a delete operation (dispose with heal) to turn this:

Into this (current healing behavior):

Or this:

Or delete the entire subtree (equivalent to block.dispose(/*don't heal*/false, /* do anim*/true);).

I don't think the first option makes any sense. The second, might seem reasonable in a few cases, but but I don't think it ever makes sense with more than one input connected, and we probably should change behavior based on the number of inputs of the deleted block. Thus leaves the last, option: delete entire branch.

[AnmAtAnm]

Splitting out the larger question of whether to heal value inputs in #2261.