ch4/ofi: tolerate transient CQ errors during MPI_Finalize

[Growl1234]

Pull Request Description

When MPI_Finalize tears down OFI resources, fi_cq_read may return transient I/O errors (e.g. -FI_EIO) due to race conditions with endpoint/connection shutdown. Currently handle_cq_error treats ALL unexpected CQ errors as fatal, causing an abort even though all user communication has already completed successfully.

This patch:

1. Adds an is_finalizing flag to the OFI global state.
2. Downgrades fatal CQ errors to non-fatal when finalizing.
3. Tolerates progress errors in the finalize drain/flush loops.

This should take care of and resolve #7760.

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[hzhou]

The abort behavior is controlled by error handler at the top of the call stack, in this case, MPI_Finalize. You can intercept the error return at any of the call stack layer before returning to MPI_Finalize, as in your following changes. There is no need for changes here.