Spring Allow @Async qualifier to be declared with a placeholder or SpEL expression

Hi, I submitted this PR to solve #27775 based on @sbrannen ’s comment.

Closes gh-27775

Comment From: sbrannen

This has been merged into main in 01214b3473c4a9e4db66b2036b3c44d6ed7f1678 and slightly revised in be8224a5909f140122a1f25bc02a769b42d11e8f.

Thanks for making your first contribution to the Spring Framework, @terminux! 👍