feat(storage): implement multiple buckets support

[phantumcode]

• [x] PR title and description conform to Pull Request guidelines.

Issue #, if available:

Description of changes: Adding multi-bucket support for Amplify Storage category/plugin. All code changes have been previously reviewed and approved:

• https://github.com/aws-amplify/amplify-android/pull/2895
• https://github.com/aws-amplify/amplify-android/pull/2896
• https://github.com/aws-amplify/amplify-android/pull/2899
• https://github.com/aws-amplify/amplify-android/pull/2900
• https://github.com/aws-amplify/amplify-android/pull/2906
• https://github.com/aws-amplify/amplify-android/pull/2908

The following commit was made to fix formatting/lint errors, no functional code changes were made: 05b21e6

How did you test these changes? Changes were manually tested, unit tested, and integration tested.

Documentation update required?

• [ ] No
• [x] Yes (https://github.com/aws-amplify/docs/pull/7918)

General Checklist

• [x] Added Unit Tests
• [x] Added Integration Tests
• [x] Security oriented best practices and standards are followed (e.g. using input sanitization, principle of least privilege, etc)

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

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 27.41935% with 225 lines in your changes missing coverage. Please review.

Project coverage is 43.96%. Comparing base (7f874ed) to head (de5fc34).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2904 +/- ## ========================================== - Coverage 44.01% 43.96% -0.06% ========================================== Files 926 931 +5 Lines 30485 30688 +203 Branches 4351 4377 +26 ========================================== + Hits 13419 13491 +72 - Misses 15601 15728 +127 - Partials 1465 1469 +4 ```