Add feature id tracking for credentials

[richardwang1124]

The SDKs would like to track customer adoption of features through feature id tracking. This PR adds tracking for newly added credentials related metrics.

Tracking will be done through the signing plugin. When the signing handler is called, we retrieve the credentials class type, determine the metrics for the credentials, and pass them to the UserAgent through the with_metric method.

---

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

1. To make sure we include your contribution in the release notes, please make sure to add description entry for your changes in the "unreleased changes" section of the CHANGELOG.md file (at corresponding gem). For the description entry, please make sure it lives in one line and starts with Feature or Issue in the correct format.

2. For generated code changes, please checkout below instructions first:
   https://github.com/aws/aws-sdk-ruby/blob/version-3/CONTRIBUTING.md

Thank you for your contribution!

[github-actions]

You have made a change to core without a corresponding change to the CHANGELOG.md. This change will not result in a new version and will not published unless an entry is added to CHANGELOG.md.

[github-actions]

You have made a change to core without a corresponding change to the CHANGELOG.md. This change will not result in a new version and will not published unless an entry is added to CHANGELOG.md.

[github-actions]

Detected 1 possible performance regressions:

• aws-sdk-dynamodb.require_mem_retained - z-score regression: 2.71 -> 2.72. Z-score: 22.55

[github-actions]

Detected 30 possible performance regressions:

• aws-sdk-dynamodb.require_mem_retained - z-score regression: 2.54 -> 2.54. Z-score: 63.76
• aws-sdk-dynamodb.require_mem_allocated - z-score regression: 10.75 -> 10.76. Z-score: 132.35
• aws-sdk-dynamodb.put_item_small_allocated_kb - z-score regression: 77.83 -> 100.64. Z-score: 21.42
• aws-sdk-dynamodb.put_item_large_allocated_kb - z-score regression: 11736.62 -> 11759.42. Z-score: 21.57
• aws-sdk-kinesis.client_mem_allocated - z-score regression: 0.62 -> 0.62. Z-score: 86.85
• aws-sdk-kinesis.put_record_small_allocated_kb - z-score regression: 48.73 -> 70.08. Z-score: 597.72
• aws-sdk-kinesis.put_record_small_ms - z-score regression: 0.45 -> 0.81. Z-score: 19.39
• aws-sdk-kinesis.put_record_large_allocated_kb - z-score regression: 196.84 -> 218.19. Z-score: 597.72
• aws-sdk-s3.client_mem_retained - z-score regression: 0.12 -> 0.12. Z-score: Infinity
• aws-sdk-s3.client_mem_allocated - z-score regression: 0.9 -> 0.9. Z-score: Infinity
• aws-sdk-s3.get_object_small_allocated_kb - z-score regression: 63.1 -> 85.49. Z-score: 20.45
• aws-sdk-s3.get_object_large_allocated_kb - z-score regression: 21568.38 -> 21590.71. Z-score: 19.37
• aws-sdk-s3.put_object_small_allocated_kb - z-score regression: 82.14 -> 102.61. Z-score: 419.84
• aws-sdk-s3.put_object_small_ms - z-score regression: 0.71 -> 1.02. Z-score: 18.28
• aws-sdk-s3.put_object_large_allocated_kb - z-score regression: 9298.43 -> 9318.97. Z-score: 248.92
• aws-sdk-s3.put_object_multipart_large_allocated_kb - z-score regression: 32122.47 -> 32207.35. Z-score: 408.5
• aws-sdk-s3.head_object_allocated_kb - z-score regression: 111.34 -> 132.76. Z-score: 268.56
• aws-sdk-sns.client_mem_retained - z-score regression: 0.1 -> 0.1. Z-score: Infinity
• aws-sdk-sns.client_mem_allocated - z-score regression: 0.58 -> 0.59. Z-score: Infinity
• aws-sdk-sns.publish_small_allocated_kb - z-score regression: 59.51 -> 81.1. Z-score: 387.39
• aws-sdk-sns.publish_small_ms - z-score regression: 0.53 -> 0.84. Z-score: 18.18
• aws-sdk-sns.publish_large_allocated_kb - z-score regression: 440.77 -> 462.1. Z-score: 303.71
• aws-sdk-cloudwatchlogs.client_mem_allocated - z-score regression: 0.59 -> 0.6. Z-score: 21.94
• aws-sdk-cloudwatchlogs.put_log_events_small_allocated_kb - z-score regression: 58.49 -> 79.83. Z-score: 424.24
• aws-sdk-cloudwatchlogs.put_log_events_small_ms - z-score regression: 0.54 -> 0.84. Z-score: 17.23
• aws-sdk-cloudwatchlogs.put_log_events_large_allocated_kb - z-score regression: 5992.49 -> 6013.79. Z-score: 391.7
• aws-sdk-core.gem_size_kb - z-score regression: 381.0 -> 383.0. Z-score: Infinity
• aws-sdk-cloudwatch.client_mem_allocated - z-score regression: 0.58 -> 0.59. Z-score: 39.15
• aws-sdk-cloudwatch.put_metric_data_small_allocated_kb - z-score regression: 59.14 -> 80.47. Z-score: 326.29
• aws-sdk-cloudwatch.put_metric_data_large_allocated_kb - z-score regression: 1535.47 -> 1556.81. Z-score: 424.24

[github-actions]

You have made a change to core without a corresponding change to the CHANGELOG.md. This change will not result in a new version and will not published unless an entry is added to CHANGELOG.md.

[github-actions]

You have made a change to core without a corresponding change to the CHANGELOG.md. This change will not result in a new version and will not published unless an entry is added to CHANGELOG.md.

[github-actions]

You have made a change to core without a corresponding change to the CHANGELOG.md. This change will not result in a new version and will not published unless an entry is added to CHANGELOG.md.

[mullermp]

Getting closer. We can chat offline if we need to. I'd like to poke at the "resolving" approach a bit more.

[jterapin]

Partial review since this is WIP

[mullermp]

Massive improvement!!! Just finishing touches.

[jterapin]

Nice! 👍 We're almost there! Credentials are a doozy to deep dive so it's great to see you power though!

[jterapin]

LGTM! Approved but I would like Matt to give the "final" lookover.

[mullermp]

Nice job! Looks clean.