Add LICENSE to generated crates and set license in Cargo.toml (#301)

...lin/software/amazon/smithy/rustsdk/AwsCodegenDecorator.kt

...n/software/amazon/smithy/rustsdk/CrateLicenseDecorator.kt

aws/sdk-codegen/src/main/resources/LICENSE

aws/sdk/build.gradle.kts

...oftware/amazon/smithy/rust/codegen/rustlang/RustWriter.kt

...are/amazon/smithy/rust/codegen/smithy/CodegenDelegator.kt

...oftware/amazon/smithy/rust/codegen/smithy/RustSettings.kt

...ithy/rust/codegen/smithy/generators/CargoTomlGenerator.kt

...tlin/software/amazon/smithy/rust/codegen/testutil/Rust.kt