Make when expression non exhaustive in EndpointBuiltInsDecorator.kt

[ysaito1001]

Motivation and Context

Updates handling matching on endpoint parameter type in EndpointBuiltInsDecorator.kt

Description

Smithy 1.48.0 will introduce ParameterType.STRING_ARRAY for the endpoint parameter type and exhaustive matching like what we have today makes lint unhappy.

codegen/src/main/kotlin/software/amazon/smithy/rustsdk/EndpointBuiltInsDecorator.kt: (113, 9): 'when' expression must be exhaustive, add necessary 'STRING_ARRAY' branch or 'else' branch instead 

For now, we will fail out loud for anything other than string or boolean since we most likely don't have services that support ParameterType.STRING_ARRAY today. The panic will let us know during internal preview when a service supports ParameterType.STRING_ARRAY.

Testing

Relies on tests in CI

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[github-actions]

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• No codegen difference in the AWS SDK
• No codegen difference in the Client Test
• No codegen difference in the Server Test
• No codegen difference in the Server Test Python
• No codegen difference in the Server Test Typescript

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