Recover PRs lost in pipeline rewrite rebase

[SydneyhSmith]

When rebasing the pipeline rewrite work we werent pulling in the changes we made, just overwriting them with rewritten code that wasn't reconciled with updates...as a result of this a number of PRs need to be rewritten/re-added to the code base. these are the PRs we know of that need to be recovererd:

• Load only bundled PSReadLine #1514
• Run new PSReadLine test on Windows #1522
• Send stopDebugger notification when appropriate #1570
• Implement LengthInBufferCells to fix ANSI formatting #1571

[andyleejordan]

Thanks for capturing these @SydneyhSmith. Good news: we've managed to already get 3/4 of these.