Arm backend: Reject symbolic shapes without shape extension

[bdemirb]

This patch prevents unsupported dynamic-shape PAD cases from being delegated to TOSA specs that do not support the shape extension.

Dynamic PAD lowering needs symbolic shape handling. When symbolic tensor shapes are serialized for a spec without the TOSA shape extension, symbolic dimensions can be emitted as -1. For PAD this can make Vela validate output shapes with checks such as -1 == -1 + 1, which reports a PAD output shape mismatch instead of rejecting the unsupported dynamic-shape case earlier.

Add a shared TOSA partitioner support check that rejects nodes with symbolic tensor input or output shapes when the active TOSA spec does not enable the shape extension. Known supported symbolic-shape cases, such as upsample_nearest2d.vec and quantize/dequantize boundaries, remain delegable. This keeps the restriction tied to the TOSA spec capability while preserving existing dynamic upsample coverage.

The regression coverage verifies that U55 and U85 dynamic PAD cases are not delegated and that static 5D PAD still delegates through Ethos-U lowering.

Signed-off-by: Baris Demir baris.demir@arm.com

Change-Id: If2912c1badcb6528c4869e5bc716aa8da136ff2a

cc @digantdesai @freddan80 @per @zingo @oscarandersson8218 @mansnils @Sebastian-Larsson @robell @rascani

[pytorch-bot]

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[bdemirb]

@pytorchbot label "partner: arm"

[bdemirb]

@pytorchbot label "release notes: arm"