[llvm] IR: Add attribute negated (PR #121027)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> Is `operand bundles` for this purpose?

Mostly not. Bundles also aren't associated with a specific operation, but for this type of usage they would have similar usability issues as attributes (adding a new side channel every user of the operation would have to consider) 

https://github.com/llvm/llvm-project/pull/121027