Set BAD_REQUEST error code for 400 error instead of UNKNOWN

[pcmoritz]

Issue #, if available:

This fixes https://github.com/aws/aws-sdk-cpp/issues/1843

More crucially, it removes the current inconsistency between boto3 and the AWS CLI on the one hand and the C++ SDK on the other hand when it comes to 400 return codes.

Description of changes:

Convert a 400 http status code into a BAD_REQUEST error instead of UNKNOWN.

This PR might need to be re-done from the Amazon side since I'm not familiar with the code generation tools used. I just fixed the occurrences manually.

Check all that applies:

• [ ] Did a review by yourself.
• [ ] Added proper tests to cover this PR. (If tests are not applicable, explain.)
• [ ] 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.

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[pcmoritz]

This PR is part of trying to improve the error messages (to the same standard as boto3) that are raised from Apache Arrow when interacting with S3: https://issues.apache.org/jira/browse/ARROW-17079