BREAKING(cli/unstable): make ProgressBar value and max properties public

[timreichen]

Ref: #6408 (comment)

This PR makes the ProgressBar value and max properties public.
This is more flexible as the progress bar max can be adjusted after instantiation and allows to set the value directly (progressBar.value = newValue) instead of only adding increments.
This makes the add() method obsolete as the same can be achieved with progressBar.value += x.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.74%. Comparing base (f8894da) to head (69bf849).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6430   +/-   ##
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  Coverage   94.74%   94.74%           
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  Files         583      583           
  Lines       46478    46478           
  Branches     6523     6523           
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  Hits        44036    44036           
  Misses       2399     2399           
  Partials       43       43           

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[kt3k]

It makes sense to me to make max modifiable as I sometimes see such progress indicator (e.g. Deno's download indicator)

It also makes sense to make value public property as it now accepts the total value number in addition to the difference. (It should be convenient when the progress source only reports the total current number.)

LGTM