chore(auth): general clean up for credentialsProvider and also rename Credentials from sdk #1225

Job	Run time
prebuild	2m 36s
license-test / License tests	22s
bundle-size-tests / Bundle size tests	1m 31s
github-actions-test / Github Action format test	26s
unit-tests / get-package-list / Get packages list	9s
unit-tests / Unit Test - @aws-amplify/adapter-nextjs	33s
unit-tests / Unit Test - @aws-amplify/analytics	43s
unit-tests / Unit Test - @aws-amplify/auth	1m 40s
unit-tests / Unit Test - aws-amplify	1m 10s
unit-tests / Unit Test - @aws-amplify/core	55s
unit-tests / Unit Test - @aws-amplify/storage	1m 11s
Unit and Bundle tests have passed	1s
	11m 17s

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