[llvm] [VPlan] Create and re-use ModuleSlotTracker for metadata printing. (PR #203982)

[Florian Hahn via llvm-commits]

fhahn wrote:

Ping. https://github.com/llvm/llvm-project/pull/220390 (https://github.com/llvm/llvm-project/commit/dd7236de4812ff2c4dc28e2b2948e3f35586d33b has simplified this a bit, as ModuleSlotTracker now also assigns stable IDs to metadata not yet inserted into a module.

https://github.com/llvm/llvm-project/pull/203982