Move cursor more wisely after removing node(s)

[lambdalisue]

Currently, the cursor moves on the root node after users remove node(s).

But it would be nice if the cursor position follows the cases below

Case 1

  |- Hello
* |- Darkness
  |- My         <-- CURSOR
* |- Old
  |- Friend

  |- Hello
  |- My         <-- CURSOR
  |- Friend

Case 2

  |- Hello
* |- Darkness
  |- My
* |- Old        <-- CURSOR
  |- Friend

  |- Hello
  |- My         <-- CURSOR
  |- Friend

Case 3

  |- Hello
* |- Darkness   <-- CURSOR
  |- My
* |- Old
  |- Friend

  |- Hello      <-- CURSOR
  |- My
  |- Friend

Case 4

  |- Hello
* |- Darkness 
* |- My
* |- Old        <-- CURSOR
  |- Friend

  |- Hello      <-- CURSOR
  |- Friend

Ref. https://vim-jp.slack.com/archives/CLKR04BEF/p1596425718256400