rust crate apache_avro_derive creates invalid schemas for raw identifiers

When using a raw identifier as field name, the `r#` prefix is used as field name for the resulting schema which results in an invalid AVRO schema.
Example:
 
 

struct TestRawIdent { r#type: bool }

 
 
I implemented a fix in https://github.com/apache/avro/pull/1945