[typescript-node] Added ability to work with `defaultHeaders` and fixed authentication

Created by: AProts

• added getter/setter for defaultHeaders property
• fixed authentication for clients that support several auth methods (use auth method only if auth credentials are set)

Issues fixed: [typescript-node][BUG] create getter/setter for defaultHeaders property #4894 [typescript-node][BUG] all supported authentication method (not configured) applied to request #4895

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