MultiProgress example indentation prefixes are sometimes not drawn

[djc]

When running cargo run --example multi-tree-ext, the indentation sometimes goes missing.

Expected output:

[32/32]   ✔ the
[32/32]     ✔ quick
[32/32]       ✔ brown
[32/32]         ✔ fox
[32/32]           ✔ jumps
[32/32]             ✔ over
[32/32]               ✔ a
[32/32]                 ✔ lazy
[32/32]                   ✔ dog
████████████████████████████████████████  585/585

Actual output:

[32/32] ✔ the
[32/32] ✔ quick
[32/32] ✔ brown
[32/32] ✔ fox
[32/32] ✔ jumps
[32/32] ✔ over
[32/32] ✔ a
[32/32] ✔ lazy
[32/32] ✔ dog
████████████████████████████████████████  585/585

Bisection points to 1d37660 as being the cause, which makes sense because it touches the prefix -- on the other hand, it's still unclear me to how those fairly straightforward changes could cause this.

[djc]

Here it seems something is different when drawing after the progress bar is finished, since the prefix seems to be correct before the progress bar is finished.

[djc]

It turns out that although #395 made sure that message and prefix are carried over even if the style is overwritten, that only fixed ProgressBar::with_style() and not ProgressBar::set_style(), which is used in this example. Thus, this issue is fixed in #414 by making those methods share the same logic from #395.

[chris-laplante]

Good catch