Replace `SmallVector<Type/Value>(n, x)` with `Repeated<Type/Value>(n,
x)`. This avoids heap allocations for repeated values.
Also change `ExtractAddressComputations` rebuild callbacks from
`ArrayRef<Value>` to `ValueRange` to enable `Repeated<Value>`
passthrough.
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>