Add Azure Developer Credential

[hemarina]

Description

• add azure developer credential and implementation
• add unit test
• change readme

WIP:
update test once tenantId is added under GetToken in azd repo

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• The pull request does not introduce [breaking changes]
• CHANGELOG is updated for new features, bug fixes or other significant changes.
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• Pull request includes test coverage for the included changes.

[azure-sdk]

API change check

APIView has identified API level changes in this PR and created following API reviews.

azure-identity

[xiangyan99]

The code change looks good.

Please fix CI failures.

[hemarina]

@xiangyan99 FYI All tests passed except for Run verifytypes. Thanks for the help from @kristapratico and we decided to skip the types for azure-identity until azure-core typing is removed from envirnoment_exclusions.py.
If this looks good, feel free to merge this PR (I don't have access to merge it).