Implement IgnoreExtraFieldsFromTextual

[passuied]

Description

• Add ability to ignore extra fields from textual representation

• Approach:

  1. A way to skip arbitrary JSON values without a codec
  2. An option to enable lenient behavior
  3. Passing this option through the codec builder chain

• Usage example:

opt := &goavro.CodecOption{
    IgnoreExtraFieldsFromTextual: true,  // Ignore unknown fields during JSON decoding
}
codec, err := goavro.NewCodecWithOptions(schema, opt)

// Now this will work even with extra fields in JSON
native, _, err := codec.NativeFromTextual([]byte(`{"knownField": "value", "unknownField": "ignored"}`))

Issue Reference

#294

[passuied]

@rockwotj Re-implemented the solution. Please review