Fix CRT constructor

[sbiscigl]

Description of changes:

Fixes a bug where client configuration was not getting created correctly in the S3CrtClient causing inconsistencies between different constructors.

Specifically that on the constructor where a credentials provider was being provided, the incorrect call was being made, causing S3Crt specific config to be lost

i.e.

#include <aws/core/Aws.h>
#include <aws/core/utils/logging/LogLevel.h>
#include <aws/s3-crt/S3CrtClient.h>

int main() {
  Aws::SDKOptions sdk_options;
  sdk_options.loggingOptions.logLevel = Aws::Utils::Logging::LogLevel::Off;
  Aws::InitAPI(sdk_options);

  Aws::S3Crt::S3CrtClientConfiguration configuration{};
  configuration.contentLengthConfiguration = Aws::S3Crt::S3CrtClientConfiguration::CONTENT_LENGTH_CONFIGURATION::SKIP_CONTENT_LENGTH;
  Aws::S3Crt::S3CrtClientConfiguration copied{configuration, Aws::Client::AWSAuthV4Signer::PayloadSigningPolicy::Never};
  if (copied.contentLengthConfiguration != Aws::S3Crt::S3CrtClientConfiguration::CONTENT_LENGTH_CONFIGURATION::SKIP_CONTENT_LENGTH) {
    std::cout << "copied incorrectly!\n";
  }

  Aws::ShutdownAPI(sdk_options);
  return 0;
}

The impact of this was customers that set SKIP_CONTENT_LENGTH would not have it honored if they provided their own credentials provider.

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.

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