Simplify CORSAdaptor

[samutamm]

Is your feature request related to a problem? Please describe.
#498 enabled both CORS pre-flight and CORS requests for CORSAdaptor while originally only CORS pre-flight requests were possible. In many cases both CORS pre-flight and CORS requests are necessary and should be enabled by default.

Describe the solution you'd like
Either

• change default value of supportCORSRequest to true
• remove supportCORSRequest and support both CORS pre-flight and CORS requests by default.

Describe alternatives you've considered

Additional context

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Thanks for contributing 🎉!

[jxd134]

I support the second measure.
Users reduce the cost of learning about cross-domain settings.

[localvar]

close as #839 resolves this issue.