Make ActiveSupport HashWithIndifferentAccess#to_options and alias for HashWithIndifferentAccess#symbolize_keys

[weilandia]

Fixes #34359

Summary

Prior to 5.2.0 (de9e323, 2cad8d7), HashWithIndifferentAccess#to_options acted as
an alias to HashWithIndifferentAccess#symbolize_keys. Now, #to_options
returns an instance of HashWithIndifferentAccess while #symbolize_keys
returns and instance of Hash.

This pr makes it so HashWithIndifferentAccess#to_options acts as an
alias for HashWithIndifferentAccess#symbolize_keys once again.

Other Information

See #34359

Thanks!

[rails-bot]

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[gmcgibbon]

I think this counts as a bug. Could you please add a changelog entry?

[weilandia]

@gmcgibbon thanks for the review! I addressed your comments -- let me know if anything else stands out.

Also, do you think this issue warrants a note in the release notes/upgrade guide for 5.2?