[LPT] Skip PadTransformation for non-finite CONSTANT pad values

[pj3iL]

Guard canBeTransformed() with checkConstantNotInf when pad mode is CONSTANT, preventing an invalid quantized constant from being created during the dequantization-move rewrite. Replace the magic input index 3 with a named constant for readability. Add a regression test covering ±inf on a unique pad dimension.

Details:

• src/common/low_precision_transformations/src/pad.cpp
• src/common/low_precision_transformations/tests/pad_transformation.cpp

Tickets:

• CVS-192736

AI Assistance:

• AI assistance used: yes
• Used to understand how int8 transformation works, creating the changes quickly for ±inf, followed by tests. Manual checks are done for correctness and validation.