Deprecate JUnit 4 utilities in the project

[artembilan]

Also, migrate JUnit 4 tests to Jupiter.
More info in: spring-projects/spring-framework#34794

[chickenchickenlove]

Hi, @artembilan .
Would it be okay if i look into this issue?
If the deadline isn’t too tight, I’d like to give it a try.

[artembilan]

Hey, @chickenchickenlove !

Be my guest!

No, deadline is not tight: the November is our GA release month.
So, all good so far.
Thanks