AVRO-3772: [Rust] Deserialize Errors for an Unknown Enum Symbol instead of Returning Default

[martin-g]

AVRO-3772

Take into account the field's default value when resolving an enum in a reader schema

What is the purpose of the change

• Fix the resolution of an enum with a symbol which is no more available in the reader schema. Use any default value if available before returning an error

See https://avro.apache.org/docs/1.11.1/specification/#schema-resolution

Verifying this change

• An old test has been updated to the new logic

Documentation

• Does this pull request introduce a new feature? no

[martin-g]

I've pushed a second commit about (I'm also curious if there would be another issue if the record contained a symbol that exists in the writer enum and had an index greater than the len of the reader's symbols since it appears to be doing a check for that on line 859).
I don't see a requirement in the specification about the number of the symbols, so I removed that.
The logic about the number of the symbols is valid only for the decode functionality.