[llvm] [Passes] Enhance `--print-pipeline-passes` (PR #202892)

[via llvm-commits]

paperchalice wrote:

> Can we make the tree still a valid pipeline by keeping `(` and `)`? That is, just make this a formatting change?

Pass pipeline string is white space sensitive, in this case the formatted pipeline string is no longer a valid pipeline string, but just print a formatted pipeline string is OK for me.

https://github.com/llvm/llvm-project/pull/202892