feat(middleware-retry): call retry strategy based on value in retryMode

[trivikr]

Issue

Internal JS-2636

Description

Call retry strategy based on value in retryMode.
This PR will be posted upstream when the following PRs are merged:

• feat(clients): add retryModeProvider in runtimeConfig aws/aws-sdk-js-v3#2440
• feat(middleware-retry): add Adaptive Retry Strategy aws/aws-sdk-js-v3#2454

Testing

Verified that adaptive retry strategy is called when retryMode is passed:

const { DynamoDB } = require("../aws-sdk-js-v3/clients/client-dynamodb");

(async () => {
  const client = new DynamoDB({ retryMode: "adaptive" });
  await client.listTables({ Limit: 1 });
})();

Verified that retryStrategy.mode was "adaptive" in retyMiddleware using console.log

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[trivikr]

PR posted upstream at aws#2456