feat(progressbar): simplify template

[VolodymyrBaydalka]

Reduced number of elements by moving "progress" class to host element. As result height can be changed via style.

[benouat]

Hey, the build is failing, you have unformatted files
Please run yarn check-format locally and have a look at what's reported there.

[maxokorokov]

Thanks for the PR!

[mradcliffe]

A couple of workarounds in case anyone else had extended NgbProgressBar and relied on a wrapper class with bootstrap's progress class to make fancy progress bars.

• Use increase specificity in CSS e.g. my-custom-progressbar.progress { }
• Set the new height property to 'auto', use HostBinding on other styles added by .progress on the component selector, use a wrapper class to reset the height to the default value because the height property applies to all elements that use .progress.
• Don't extend NgbProgressBar, re-write everything from scratch using bootstrap classes directly.