feat(auth): Expose AuthConfiguration directly

[mattcreaser]

• PR title and description conform to Pull Request guidelines.

Issue #, if available:

Description of changes:
Amplify previously exposed raw JSON via getPluginConfiguration for Authenticator to consume. This change instead exposed a pre-parsed AuthConfiguration.

• Added signupAttributes, usernameAttributes, verificationMechanisms, and passwordProtectionSettings to AuthConfiguration
• Exposed AuthConfiguration and related types with @InternalAmplifyApi annotations.
• Deprecated existing getPluginConfiguration function.
• Moved AuthConfiguration to com.amplifyframework.auth.cognito package. This is a more appropriate location for this class.

Equivalent Swift PR is here: aws-amplify/amplify-swift#3566

How did you test these changes?

• Tested consuming new internal API in Authenticator

Documentation update required?

• No
• Yes (Please include a PR link for the documentation update)

General Checklist

• Added Unit Tests
• Added Integration Tests
• 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-commenter]

Codecov Report

Attention: Patch coverage is 84.21053% with 15 lines in your changes are missing coverage. Please review.

Project coverage is 43.02%. Comparing base (b448ecc) to head (09727c9).

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2740      +/-   ##
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+ Coverage   42.92%   43.02%   +0.10%     
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  Files         905      905              
  Lines       29127    29178      +51     
  Branches     4144     4152       +8     
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+ Hits        12503    12555      +52     
+ Misses      15268    15265       -3     
- Partials     1356     1358       +2     

[tylerjroach]

Looks good, but thoughts on removing the Java style builders since those are all internal?

[mattcreaser]

The builders are only used from tests and could be removed, but I'd do that separately to avoid bloating this PR.