Upgrade to the latest Bootstrap version

[mkArtakMSFT]

There were several breaking changes in Bootstrap 4 (from Bootstrap 3) which we also need to react to as part of this upgrade.

This issue will also be used to track all related work to the bootstrap 5 update:

• identity ui/scaffolding
• project template fixes

[KKacer]

I think Bootstrap was past!
By the all recent changes and news in CSS, there is no need for bootstrap.
tying more and more the platform and components to a 3rd party library will add more time and hassle for people who try to make more pure or more customized things.
I believe BootStrap was past though Blazor can be the future.
So if possible while you try to consider the needs of web newbies, consider 1 extra scenario without Bootstrap, Materialize, and font-awesome, Jquery things, which none of them are standards, they may make a buzz for a period and then be gone, and each person can have it's own choice or custom scenario.
So personally I suggest not invest on bootsrap much, just may be there as an option, instead invest more on the standards. Like considering CSS Grid, FlexBox, ...

[mkArtakMSFT]

Thanks for your feedback @KKacer.
We'll definitely think about these points you've mentioned when we will get to handling this issue.

[mkArtakMSFT]

Related #23017