Update to Smithy 1.39 (#2998)

## Motivation and Context
<!--- Why is this change required? What problem does it solve? -->
<!--- If it fixes an open issue, please link to the issue here -->
Upgrade to Smithy 1.39:



## Description
<!--- Describe your changes in detail -->
The main change here is updating the endpoints generator. To get
everything building I had to make a couple of other changes:
- disable a couple of broken protocol tests
- update the models so that they pass the new, more stringent validators
- clean up some of our test models that were invalid
- delete some protocol tests that were migrated upstream

## Testing
<!--- Please describe in detail how you tested your changes -->
<!--- Include details of your testing environment, and the tests you ran
to -->
<!--- see how your change affects other areas of the code, etc. -->
CI / verify no codegen diff.
- [ ] verify no diff

## Checklist
<!--- If a checkbox below is not applicable, then please DELETE it
rather than leaving it unchecked -->
- [ ] 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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choice._

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Co-authored-by: kstich <kevin@kstich.com>