VSCodeVim Undo stack should be synced with VSCode undo stack

VSCodeVim undo is not synced with VSCode undo. I've provided a couple different issues/test cases below to illustrate what I mean:

Simple undo
VSCode and VSCodeVim seem to maintain different undo stacks, such that pressing u in VIM adds to the VSCode undo stack so that doing a VSCode undo (CMD-Z) undoes the VIM undo. u and CMD-Z should have the same function and share a common undo stack.

Search Replace
When doing a vim-based search and replace, one change with all the replacements is pushed to the VSCodeVim undo stack, whereas one change for each replacement is pushed to the VSCode undo stack. It's easy to get confused about the state of the document if you make a replacement, then press CMD-Z thinking you've reversed all the changes, make some other changes, then have to backtrack to revert the rest of the replacements.

I'm not familiar with the extension architecture for VSCode, so I'm not sure what is technically possible here.

I can break these off into separate issues if you'd prefer.

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Simple undo

What did you do?
Press i. Type some text: PIZZA. Press escape. Press i. Type some more text: IS GREAT. Press the u key to undo. Press CMD-Z.

What did you expect to happen?
" IS GREAT" should disappear upon pressing u. "PIZZA" should disappear upon pressing CMD-Z so we're left with an empty string.

What happened instead?
" IS GREAT" disappeared and then reappeared upon pressing CMD-Z so we're left with "PIZZA IS GREAT".

Search and replace

What did you do?
Given a 50-line document with the string "Pizza" on each line, type %s/Pizza/Hot Dogs/ from the VSCodeVim command line. Press CMD-Z.

What did you expect to happen?
"Pizza" should appear on every line.

What happened instead?
"Hot Dogs" appears on every line except the last one which shows "Pizza". Similarly, if you first undo with u then press CMD-Z, "Pizza" appears on every line except the first one which shows "Hot Dogs".

Technical details:

• VSCode Version: 1.11.1
• VsCodeVim Version: 0.6.14
• OS: MacOS 10.11.6

Start by reproducing the Simple undo and Search and replace cases in VSCodeVim with the listed VSCode and extension versions. Trace how the Vim command line and the u command interact with VSCode's undo behavior. Done means Vim undo and CMD-Z share a consistent stack, including replacement operations, without reapplying earlier edits.