[C++] SDKs to track feature Ids for Credentials (ENV)

[kai-ion]

Issue #, if available:

Description of changes:

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.

Check which platforms you have built SDK on to verify the correctness of this PR.

• Linux
• Windows
• Android
• MacOS
• IOS
• Other Platforms

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[sbiscigl]

no this isnt what we want to be doing, taking a look at the existing user agent

user-agent: 
  aws-sdk-cpp/1.11.635 
  ua/2.1 
  api/S3 
  os/Darwin#24.6.0 
  lang/c++#C++11 
  md/aws-crt#0.33.4 
  md/arch#arm64 
  md/Clang#17.0.0 
  m/D,Z,b,P

what we want to add md/override_get_credentials to see if the actual method was overrode

[sbiscigl]

this is kind of sketchy lets find the business metrics value in the user agent and re-assemble it.

auto userAgentParsed = Utils::StringUtils::Split(userAgent, ' ');
auto metricsSegment = std::find_if(userAgentParsed.begin(), userAgentParsed.end(), [](const Aws::String & value) { return value.find("m/") != Aws::String::npos; });
if (metricsSegment != userAgentParsed.end()) {
  *metricsSegment = Aws::String{*metricsSegment + ",whatever_you_want"};
  request.SetHeaderValue(USER_AGENT,
    std::accumulate(std::next(userAgentParsed.begin()), userAgentParsed.end(), userAgentParsed.front(),
      [](const std::string& a, const std::string& b) {
        return a + "," + b;
      }));
} else {
  request.SetHeaderValue(USER_AGENT, Aws::String{request.GetHeaderValue(USER_AGENT) + ",whatever_you_want" });
}