Fix tiny_map from_iter where one operation was being dropped (#2733)

## Motivation and Context
15th operation was being dropped when iterator was being read into a
TinyMap

## Description
The 15th operation was being dropped when the if statement was caught
because the operation had been popped of the iterator but hadn't been
added to the vec of operations before the two iterators were being
chained and collected into a

## Testing
Added unit tests that reproduced the issue and verified that the issue
is fixed

## Checklist
<!--- If a checkbox below is not applicable, then please DELETE it
rather than leaving it unchecked -->
- [x] I have updated `CHANGELOG.next.toml` if I made changes to the
smithy-rs codegen or runtime crates
- [ ] I have updated `CHANGELOG.next.toml` if I made changes to the AWS
SDK, generated SDK code, or SDK runtime crates

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Co-authored-by: david-perez <d@vidp.dev>
Co-authored-by: Fahad Zubair <fahadzubair@gmail.com>