Add more detailed documentation for ExtendsAutoValue, including recommendations for what users should do instead.
Add more detailed documentation for ExtendsAutoValue, including recommendations
for what users should do instead.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=282808887

google/error-prone,cushon/error-prone,cushon/error-prone,cushon/error-prone,google/error-prone,cushon/error-prone