[flang] [llvm] [reland][flang] Add ETIME runtime and lowering intrinsics implementation (PR #92571)

[jiajie zhang via llvm-commits]

JumpMasterJJ wrote:

> This adds `etime-function.mlir` to the top-level directory. Is that what you meant to do?

No, it was a mistake to add 'etime-function.mlir' to the top-level directory. I will correct this. Thank you for pointing it out.

https://github.com/llvm/llvm-project/pull/92571