Migrate adding alloca_scope to scf passes (for parallel with NNPA)

[AlexandreEichenberger]

Previous approach of adding alloca_scope at the affine level did not work for NNPA as additional passes of canonicalize were called between adding alloca_scope and handling of buffers when generating NNPA code.

This problem is fixed here by migrating that pass to work with scf and calling that pass just before handling buffers.

Once this is well established, we should probably remove the old pass at the affine level as its unlikely to be useful anymore.

With this fix, Roberta passes with NNPA:

CheckONNXModel.py -m roberta-base-11.onnx -r="-O3 -mcpu=z16 -maccel=NNPA" -a="--parallel" --shape-info=0:8x384 

> Reference command:  /workdir/onnx-mlir/build/Debug/../../utils/RunONNXModel.py --compile-args="-O3 -mcpu=z16 -maccel=NNPA" --save-ref=check-ref --shape-info=0:8x384 --seed=42 --model=roberta-base-11.onnx
>   Successfully ran the reference example, saved refs in "check-ref".

> Test command:  /workdir/onnx-mlir/build/Debug/../../utils/RunONNXModel.py --compile-args="-O3 -mcpu=z16 -maccel=NNPA --parallel" --load-ref=check-ref --verify=ref --verify-every-value --model=roberta-base-11.onnx
>   Successfully ran the test example and verified against "check-ref".

[tungld]

LGTM.

[jenkins-droid]

Jenkins Linux s390x Build #13914 [push] Migrate adding alloca_sc... started at 10:13

[jenkins-droid]

Jenkins Linux ppc64le Build #12911 [push] Migrate adding alloca_sc... started at 10:22

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Jenkins Linux amd64 Build #13887 [push] Migrate adding alloca_sc... started at 09:13

[jenkins-droid]

Jenkins Linux amd64 Build #13887 [push] Migrate adding alloca_sc... passed after 1 hr 10 min

[jenkins-droid]

Jenkins Linux s390x Build #13914 [push] Migrate adding alloca_sc... passed after 1 hr 35 min

[jenkins-droid]

Jenkins Linux ppc64le Build #12911 [push] Migrate adding alloca_sc... passed after 1 hr 55 min