[protobuf-schema] Replace zero value enum suffix from UNKNOWN to UNSPECIFIED

[lucy66hw]

ref #20472
Based on protobuf style guide The zero value enum should have the suffix UNSPECIFIED.

• Changed protobuf CONFIG OPTIONS from startEnumsWithUnknown to startEnumsWithUnspecified.
• ENUM zero value change to UNSPECIFIED suffix.

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[reta]

@lucy66hw just a question please, reading the https://protobuf.dev/best-practices/dos-donts/#unspecified-enum. it seems like the right name for first element should have UNSPECIFIED suffix, fe <enum_name>_UNSPECIFIED. Shouldn't we follow this convention? Thank you.

[lucy66hw]

@reta thanks for comment. yes, this is the target of the PR. It replaces the current zero enum suffix from UNKNOWN to UNSPECIFIED. The enum_name prefix will be added by function addEnumValuesPrefix, resulting in the zero enum being named <enum_name>_UNSPECIFIED

[reta]

@wing328 wondering if you could find a time to look into this small change, thank you

[amberzsy]

@wing328 could you look into this pr?