Cleanup ASN1 API - Githubissues

Integer typealias is now a member of ASN1, and used throughout code in place of BigInt.
AnyTag typealias is now used instead of UInt8
ASN1.unwrapped now fully unwraps values to Swift types
ASN1 value accessors now return PotentASN1 module types in place of tuples.
Renamed DERReader to ASN1DerReader and DERWriter to ASN1DERWriter
TaggedValue protocol renamed to Tagged
Previously private Tagged struct is now a public type named TaggedValue

outfoxx / PotentCodables