[mlir][spirv][memref] Calculate alignment for `PhysicalStorageBuffer`s (#80243)

The SPIR-V spec requires that memory accesses to
`PhysicalStorageBuffer`s are annotated with appropriate alignment
attributes [1]. Calculate these based on memref alignment attributes or
scalar type sizes.

[1] Otherwise spirv-val complains:
```
[VULKAN] ! Validation Error: [ VUID-VkShaderModuleCreateInfo-pCode-01379 ] | MessageID = 0x2a1bf17f | SPIR-V module not valid: [VUID-StandaloneSpirv-PhysicalStorageBuffer64-04708] Memory accesses with PhysicalStorageBuffer must use Aligned.
  %48 = OpLoad %float %47
```