[aws-cpp-sdk-s3-crt] support for the exponential back-off retry strategy

[grrtrr]

The S3CrtClient not longer has a configurable retry strategy.

By default, the S3CrtClient uses the 'standard' AWS retry strategy with default parameters (5 maximum retries, scale factor of 25msec and default/full jitter options).

In porting from S3Client to S3CrtClient deployments, support for exponential back-off is necessary, in order to retry for a longer period.

This is based on the truncated exponential backoff in https://github.com/awslabs/aws-c-io/pull/587.

Check all that applies:

• [X] Did a review by yourself.
• [X] Added proper tests to cover this PR. (If tests are not applicable, explain.)
• [X] Checked if this PR is a breaking (APIs have been changed) change.
• [X] Checked if this PR will not introduce cross-platform inconsistent behavior.
• [X] Checked if this PR would require a ReadMe/Wiki update.

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[jmklix]

Can you add an enum flag to opt in to this new retry strategy?

[grrtrr]

@jmklix - how would that look like in the bigger picture of the remaining configuration? For instance, setting exponentialBackoffTotalRetries to 0 disables retries.

[jmklix]

It would look like this:

enum class AwsS3CrtRetryStrategy
  {
    DEFAULT=0, /* defaults to standard now but may change */
    STANDARD,
    EXPONENTIAL_BACKOFF,
    NO_RETRY=-1,
  };

[grrtrr]

It would look like this:

Ok thanks. It may take a few weeks to implement this, I don't have time to get into that at the moment.

[grrtrr]

@jmklix - sorry it has taken a while. I have added an enum flag as requested, specifically

• used capital snake-case naming, for consistency with US_EAST_1_REGIONAL_ENDPOINT_OPTION in include/aws/s3-crt/S3CrtClientConfiguration.h,
• changed parameter names to match those of the updated https://github.com/awslabs/aws-c-io/pull/587.

[jmklix]

Thanks for taking the time to make this PR, but it's no longer necessary. We added a S3 CRT retry strategy config with this PR: https://github.com/aws/aws-sdk-cpp/pull/3110. Please let us know if there are any additional things that you would like added to this sdk.