refactor!: replace default HTTP client engine

[aajtodd]

Issue #

sibling: smithy-lang/smithy-kotlin#606

Description of changes

This PR swaps the default client HTTP engine from the CRT one to an opaque KMP compatible engine. The new default is one backed by Ktor/OkHttp. The existing CRT engine can still be used if desired but requires explicitly setting it.

Also in this PR is a modification of some of the e2e tests. The "big list of naughty" strings has been removed from S3 presign tests. These are not particularly representative of real object keys and are not recommended by S3 guidelines on object key naming. I've replaced it with a simpler test. We can add to this as needed. The presign tests now execute against the default and CRT engine to ensure we aren't introducing regressions across the HTTP engines we explicitly support.

Breaking Change

This change is technically not a breaking change in API but may result in a change in behavior or exceptions seen by users. If you wish to continue using the CRT based HTTP engine you can explicitly configure it:

1. Add the dependency to your project e.g. implementation("aws.smithy.kotlin:http-client-engine-crt:0.7.9")
2. Explicitly provide the engine when creating a client

val engine = CrtEngine()
val s3 = S3Client {
    ...
    httpClientEngine = engine
}

...

// NOTE: in addition to the service client you are now responsible for the lifetime of the engine as well
s3.close()
engine.close()

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

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[ianbotsf]

Comment: Possibly cleaner:

val PRINTABLE_CHARS = (32..127).map(Int::toChar).joinToString("")

[sonarqubecloud]

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A new generated diff is ready to view: __generated-main...__generated-default-engine