[llvm] [mlir] [mlir] Mark `isa/dyn_cast/cast/...` member functions deprecated. (PR #90413)

[Christian Sigg via llvm-commits]

chsigg wrote:

Note that this change previously broke a [Windows build](https://lab.llvm.org/buildbot/#/builders/216/builds/38157).

@dyung, could you please advise how to test this change so I don't break it again? 

https://github.com/llvm/llvm-project/pull/90413