feat(vpto): extend post-update ops

[yexiaosu]

Summary

Implement Step 4 of VPTOSoftPostUpdate for issue #941: extend the VPTO post-update contract, soft-pass rewriting, and LLVM lowering to nine additional A5 memory operations:

• pto.vldsx2
• pto.vsldb
• pto.plds
• pto.pldi
• pto.psts
• pto.psti
• pto.sprsts
• pto.sprsti
• pto.vstas

This builds on the loop and sequential analyses introduced in the previous steps and reuses the same generic rewriting infrastructure.

Key changes

• Add optional updated_base results and corresponding verification.
• Extend loop and sequential soft-post-update rewriting to the nine operations.
• Model operation-specific address units:
  • element: vldsx2, vstas
  • 32-byte block: vsldb
  • byte: plds, psts, sprsts
  • target-dependent alignment: pldi, psti, sprsti
• Add A5 DIST-dependent predicate alignment rules.
• Preserve signed SPR offsets and normalize i32 offsets before pto.addptr.

Test coverage

Add lit coverage for IR verification, soft-pass rewriting, address-unit conversion, intrinsic ABI, both LLVM emitters, unsupported targets, and mixed-unit regressions.

Add seven A5 runtime cases covering direct post forms and normal-to-post soft-pass conversion.

Validation

• PTOAS build: PASS
• Focused lit tests: PASS
• CANN 9.0.0 and beta1 LLVM checks: PASS
• A5 SIM runtime cases: 7/7 passed