add user agent business metric for account id endpoints

[sbiscigl]

Description of changes:

Adds business metrics for the account id endpoint feature. Moves account id configuraiton from client specific paramters to general parameters as we should have initially.

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• 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.
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[sbiscigl]

interesting fact -- this meant functionally that the disableIMDSv1 configuration did not work if a user set a region in configuration

[SergeyRyabinin]

the comparison is done by

strcmp(mapping.first, accountIdMode.c_str()) == 0; });

i.e. not case insensitive.

In an ideal world, I'd suggest to use an enum here.
On practice, please just add a comment with possible allowed values and the requirements of the lowercase.

[sbiscigl]

I agree this is a better user experience, however this would be backwards breaking because on main because of how codegen is currently generating it.

#include <aws/core/Aws.h>
#include <aws/dynamodb/DynamoDBClient.h>

using namespace Aws;
using namespace Aws::DynamoDB;

auto main() -> int {
  SDKOptions options;
  InitAPI(options);
  {
    DynamoDBClientConfiguration config;
    config.accountIdEndpointMode = "preferred";
    DynamoDBClient client{config};
  }
  ShutdownAPI(options);
  return 0;
}

In an ideal world/On practice

yep yep, will add comment regarding