[6.0][IRGen] Fix alignment for imported C types in CVW

[drexin]

Explanation: When an imported C type is over or under aligned, we did not use the alignment of the type, but computed the maximum alignment of its components, causing alignment issues in compact value witnesses. Scope: Compact value witnesses Original PR: https://github.com/apple/swift/pull/73405 Risk: Low, only affects compact value witnesses Testing: Added test that observed the issue before the fix and does not with it. Issue: rdar://127279770 Reviewer: @mikeash

[drexin]

@swift-ci test