Tracking issue for breaking changes for ProgressBar

[kt3k]

We are planning to make the breaking changes below for ProgressBar unstable API:

• BREAKING(cli/unstable): rename ProgressBar end() method to stop() #6406
• BREAKING(cli/unstable): make ProgressBar writable optional #6409
• BREAKING(cli/unstable): make ProgressBar value and max properties public #6430

The changes below could also be related:

• refactor(cli/unstable): make ProgressBar options optional #6407
• feat(cli/unstable): add ProgressBar start() method #6408

[kt3k]

I think we first need to settle on #6407 to start landing these changes

[BlackAsLight]

On a somewhat related, somewhat different direction, both ProgressBar and Spinner have a flaw in their design in two ways.

1. You can't print other things to the console at the same time without it becoming a mess.
2. Their existence as a class gives the impression that you can have multiple running at a time, but doing so would make a mess of the terminal as they all try and overwrite each other.

I think their design needs to be reworked entirely to resolve these issues. I believe the first issue can be fixed by using some different terminal control sequences to move the cursor for rewrites instead of clearing the current line before writing again. For the second issue, I think it would be better if the APIs acted as if they were controlling some global state and not creating a piece of memory to be passed around. With this global state type of design, we could also allow more complex outputs in the terminal like multiple progress bars/ spinners or possibly even getting user input while a progress bar also updates on screen.

[timreichen]

A few other things I noticed:

• ProgressBarOptions.fmt is an abbreviation which is not very web-apish. Maybe it should be called something like formatter or format instead.
• ProgressBarFormatter seems overly complex atm. styledTime and styledData seem like they could be getters instead of functions.
• ProgressBarFormatter progressBar, styledTime and styledData should be strings without a trailing whitespaces.