Upgrade Smithy to 1.50.0

[ysaito1001]

Motivation and Context

This PR upgrades Smithy to 1.50.0. The majority of the changes follow TODO added in https://github.com/smithy-lang/smithy-rs/pull/3690. Other than that, a few adjustments needed to be made:

• for the client
  • added two failing tests RestJsonClientPopulatesDefaultValuesInInput and RestJsonClientUsesExplicitlyProvidedMemberValuesOverDefaults to known failing tests for the same reason here
  • added one broken test (i.e. the upstream test definition is incorrect but our implementation is correct) known failing tests per smithy#2341
• for the server
  • removed rest-xml-extras.smithy since RestXmlMustSupportParametersInContentType is now available upstream Smithy 1.50.0

Testing

Existing tests in CI

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[github-actions[bot]]

A new generated diff is ready to view.

• No codegen difference in the AWS SDK
• Client Test (ignoring whitespace)
• Server Test (ignoring whitespace)
• Server Test Python (ignoring whitespace)
• No codegen difference in the Server Test Typescript

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