Feature request
Would like to suggest the following feature.
The enabling of @JsonAlias for enums.

Why?
Enabling @JsonAlias for enums can help users that are faced with legacy properties.

Assume that version 0.1.0 has:

{
  "key": "stringvalue"
}

and version 0.2.0 has:

{
  "key": "stringValue"
}

Assume both are valid values and we want to map them to one Enum value. Having @JsonAlias available for this purpose can help to avoid bloat-code or custom de-serializers that do this.

Current behaviour
Not implemented.

Expected behaviour
I'd assume the same behaviour as with class members applies. So using @JsonProperty and @JsonAlias combined would yield the same result except for values not keys.

Example

public enum MyEnum{
    @JsonProperty("stringvalue") //<- Value Jackson should use during serialization and de-serialization.
    @JsonAlias({"stringValue"}) //<- Additional value, valid only during de-serialization.
    STRING_VALUE //<- Would assume "string_value" is ignored and not added to the list of valid values
}

Extra information
Version: 2.9
Occurs in patch: Yes
Feature request was also mentioned in: this issue (Couldn't find the accompanying Feature request)