str_view_all behaves poorly within Notebooks

[kevinushey]

rstudio/rstudio#2174
rstudio/rstudio#2533

Rather than allowing the widget to grow in height unboundedly with a large number of matches, perhaps the widget should instead clamp its contents to a div with a maximum height, and allow for internal scrolling? (Note that this scrolling won't work within the IDE but would work within the rendered document)