Updated nav/navset API names

[gadenbuie]

In rstudio/bslib#546, we renamed many of the nav_*() and navset_*() functions in the R API. Many of these now align with the Python naming, but there are some notable differences. Here's a summary table:

bslib (new)	Python (current)	Changes?
nav_panel()	ui.nav	👀
nav_panel_hidden()	ui.nav_content	👀 ❗
navset_tab()	ui.navset_tab
navset_pill()	ui.navset_pill
navset_pill_list()	ui.navset_pill_list
navset_hidden()	ui.navset_hidden	❗
navset_bar()	ui.navset_bar	❗
navset_card_tab()	ui.navset_tab_card	👀
navset_card_pill()	ui.navset_pill_card	👀

👀 new R name is different from current Python
❗ not in API refs

Note that this research also uncovered that ui.navset_bar and ui.navset_tab_card are exported but don't appear in the API reference.

### Tasks
- [x] `navset_pill_card` -> `navset_card_pill`
- [x] `navset_tab_card` -> `navset_card_tab`
- [x] ~~`nav_content` -> `nav_panel_hidden`~~
- [ ] `nav` -> `nav_panel`
- [x] document `navset_bar`
- [x] document `navset_hidden`
- [x] ~~document `nav_panel_hidden`~~

[schloerke]

nav_content -> nav_panel_hidden will not happen as nav_content was removed in #136

[schloerke]

@gadenbuie Would you be ok with leaving nav in py-shiny? This change would not be an easy transition.

Current methods (including deprecated methods):

>>> shiny.ui.n<TAB>
shiny.ui.nav(                 shiny.ui.navset_card_pill(    shiny.ui.navset_pill_list(   
shiny.ui.nav_control(         shiny.ui.navset_card_tab(     shiny.ui.navset_tab(         
shiny.ui.nav_menu(            shiny.ui.navset_hidden(       shiny.ui.navset_tab_card(    
shiny.ui.nav_spacer()         shiny.ui.navset_pill(         shiny.ui.notification_remove(
shiny.ui.navset_bar(          shiny.ui.navset_pill_card(    shiny.ui.notification_show(  

[cpsievert]

Reopening this as I think we should consider having a nav_panel() alias for nav() (and possibly deprecating the latter)

[wch]

I also prefer nav_panel to nav.