ErrorCode is not correct

[cmelchior]

The enum names for the Realm Object Server error codes in ErrorCode.java seems to have diverged from their current meaning.

This is unfortunate as it is most likely a breaking change to fix it, but we need to update them regardless so they are accurate.

Example is BAD_SERVER_VERSION_DOWNLOAD(111) which is bad_changeset_header_syntax(111)

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EDIT: This is actually more severe than that. Core reports errors using (category, code), but only the code is sent to Java, this means that some errors are not being mapped correctly. We need to fix this so error mapping are done using both the error code and category