[llvm] [llvm][CodeGen] Address the issue of multiple resource reservations in window scheduling (PR #100301)

[Kai Yan via llvm-commits]

kaiyan96 wrote:

We identified an issue with multiple resource reservations in window scheduling:
* This was overlooked in  [#99454](https://github.com/llvm/llvm-project/pull/99454/commits) when the PR was separated from [#99429](https://github.com/llvm/llvm-project/pull/99429).
* This issue does not affect the initiation interval calculation, as reserveResources will fail to reserve a resource that has already been reserved.
* The problem is difficult to describe at the IR level, making it challenging to create a corresponding test case.

https://github.com/llvm/llvm-project/pull/100301