Make the source compile with SIP-56 match types, for Scala 3.4.

[sjrd]

Refine the definition of EnumerationUtil.Aux to make it comply with the legal match types of SIP-56. Although weird, it is the "standard" trick for extracting enumeration Value's uner SIP-56.

Refine the result type of EnumerationReader.findEnumValue to be path-dependent instead of using the match type. It is strictly more precise.

Ref scala/improvement-proposals#65, scala/scala3#18262

[soronpo]

OMG, I didn't even know this syntax was possible

[sjrd]

{ type Value } is implicitly AnyRef { type Value}. It's a valid type. Then we create another refinement of that type, so { type Value } { type Value = A } is (AnyRef { type Value }) { type Value = A }. There's nothing surprising if you follow the grammar.