[REQ][typescript-fetch] Accept promises for bearer token in fetch

Created by: minorai

Is your feature request related to a problem? Please describe.

I want to be able to supply access tokens to APIs from MSAL library which are acquired in asynchronous manner:

const response = await msalInstance.acquireTokenSilent({
        ...loginRequest,
        account: account
    })

Describe the solution you'd like

I want for configuration parameters to accept asynchronous function

export interface ConfigurationParameters {
    // ....
    accessToken?: string | Promise<string> | ((name?: string, scopes?: string[]) => string) | ((name?: string, scopes?: string[]) => Promise<string>); // parameter for oauth2 security
    // ....
}

Describe alternatives you've considered

Where aren't any alternatives that I am aware of except for switching for another request framework or regenerating API objects on new tokens.

Additional context

This issue is identical to #7105 (closed) only for fetch instead of axios