[cuda.compute]: fix alignment not being set properly for gpu_struct types

[NaderAlAwar]

Description

Prior to this PR, the alignment for a gpu_struct like this

@gpu_struct
class pair:
    first: np.float32
    second: np.float32

is being passed as 1 to c.parallel when it is supposed to be 4. This PR fixes that.

Checklist

• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[oleksandr-pavlyk]

LGTM. A test would be nice to have. Perhaps no the correctness test, but a test than retrieves iterator and checks that alignment is as expected

[github-actions]

🥳 CI Workflow Results

🟩 Finished in 1h 12m: Pass: 100%/48 | Total: 13h 11m | Max: 47m 23s

See results here.