Switch to Font Awesome 6 icon names

[ismirsehregal]

Same procedure as described here:

https://github.com/dreamRs/shinyWidgets/pull/516#issue-1320737774

[CLAassistant]

All committers have signed the CLA.

[cpsievert]

Thanks @ismirsehregal, do you know if any of the current examples will fail with {fontawesome} 0.3.0? If not, I don't think we need to make these changes right away, but if/when we do, we should be requiring fontawesome >= 0.3.0 in the DESCRIPTION

[ismirsehregal]

Hi, @cpsievert no the current examples won't fail with {fontawesome} 0.3.0.

This is just to avoid warnings like:

This Font Awesome icon ('level-up-alt') does not exist:
* if providing a custom `html_dependency` these `name` checks can 
  be deactivated with `verify_fa = FALSE`

Accordingly, it is not urgent to merge this PR.

Cheers

[ismirsehregal]

The latest version of {fontawesome} allows to reference icons by several of their previous names. Leaving this open in case you still want to update the icon names, otherwise feel free to close the PR.