Fix S3 CRT async request lifetime

[FranciscoMaxwell]

Issue #, if available:
Fixes #3881

Description of changes:
This updates the S3 CRT async callback state to keep the original service request alive until the CRT shutdown callback runs.

Previously, CrtRequestCallbackUserData stored originalRequest as a raw pointer to the request reference passed into CopyObjectAsync, GetObjectAsync, and PutObjectAsync. Those async methods can return before the CRT callbacks finish, leaving headers/body/progress/shutdown callbacks with a dangling pointer when they access GetContinueRequestHandler() or pass the typed request to the user response handler.

The callback data now owns a shared_ptr copy of the request. InitCommonCrtRequestOption receives and stores that shared_ptr, and the shutdown callbacks use the owned request when invoking the user handler.

Check all that applies:

• Did a review by yourself.
• Added proper tests to cover this PR. (No new unit test was added; this lifetime issue depends on the async CRT request lifecycle. I verified the affected target builds successfully.)
• Checked if this PR is a breaking (APIs have been changed) change.
• Checked if this PR will not introduce cross-platform inconsistent behavior.
• Checked if this PR would require a ReadMe/Wiki update.

Check which platforms you have built SDK on to verify the correctness of this PR.

• Linux
• Windows
• Android
• MacOS
• IOS
• Other Platforms

Testing:

• git diff --check
• cmake -S . -B build-s3crt -DBUILD_ONLY=s3-crt -DENABLE_TESTING=OFF -DAUTORUN_UNIT_TESTS=OFF
• cmake --build build-s3crt --config Release --target aws-cpp-sdk-s3-crt -- /m

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[sbiscigl]

looks good to me outside two things:

• i left a comment about using a unique pointer instead of shared
• you only apply the on the CopyObject operation and none of the other bound out aws-c-s3 funcitons. you can fix this by editing the templates that generate the client code.

beyond those two things i am good to merge this barring anything that may turn up in CI

[sbiscigl]

does this need to be a shared_ptr? since we are purely life time extending it why not use Aws::UniquePtr like we do for checksumConfig?

[FranciscoMaxwell]

Thanks for the feedback. I have updated the PR accordingly.

• Replaced the request ownership in CrtRequestCallbackUserData and InitCommonCrtRequestOption with Aws::UniquePtr<Aws::AmazonWebServiceRequest>. A single callback context owns the request for its full lifetime, so shared ownership is unnecessary. The callback still exposes the request as a const view.
• Kept the UniquePtr element type non-const because the AWS allocator/deleter performs a polymorphic dynamic_cast<void*> during destruction; a const element type does not compile on MSVC.
• Applied the ownership transfer in both S3 CRT generation templates (regular and Smithy), so generated S3 CRT async operations consistently retain their request instead of limiting the change to CopyObject. The checked-in generated S3 CRT client was updated to match.

Validated with:
cmake --build build-s3crt --config Release --target aws-cpp-sdk-s3-crt -- /m:1

The updated signed commit is abf744c82.

[sbiscigl]

due to process reasons I created a PR with your commit on it, we will merge it from there