chore(config): use registry.AuthConfig everywhere possible and deprecated config.AuthConfig

[ndeloof]

What does this PR do?

use registry.AuthConfig everywhere possible and deprecated config.AuthConfig

Why is it important?

this reduce coupling with config module, relying on existing docker API types (strictly equivalent)

[Copilot]

Pull Request Overview

This PR refactors the codebase to use registry.AuthConfig from the Docker API instead of the local config.AuthConfig type, reducing coupling with the config module and leveraging existing Docker API types.

• Replaces config.AuthConfig with registry.AuthConfig throughout the codebase
• Updates the config.AuthConfig type to be an alias to registry.AuthConfig and marks it as deprecated
• Simplifies adapter functions since the types are now equivalent

Reviewed Changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
config/types.go	Converts AuthConfig to an alias of registry.AuthConfig and marks it deprecated
config/auth.go	Updates function signatures and removes redundant conversion methods
config/config.go	Updates all internal usage to registry.AuthConfig type
config/auth_test.go	Updates test cases to use registry.AuthConfig
config/config_test.go	Updates test configurations to use registry.AuthConfig
config/config_benchmarks_test.go	Updates benchmark configurations to use registry.AuthConfig
config/credentials_helpers.go	Updates credential helper function to return registry.AuthConfig
legacyadapters/config/auth.go	Simplifies adapter functions since types are now equivalent
legacyadapters/config/auth_test.go	Updates test cases to use registry.AuthConfig
legacyadapters/README.md	Updates documentation examples to use registry.AuthConfig

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[mdelapenya]

LGTM, thanks!