Add Named Placeholders for Query Printout

[deusaquilus]

Version: (e.g. 3.4.8)
Module: (e.g. quill-sql)
Database: (e.g. mysql)

Right now, for the compile-time query printout, all lifted variables are question marks:

val ctx = new SqlMirrorContext(SQLServerDialect, SnakeCase)
import ctx._
case class Person(name:String, age:Long)
val nameValue = "Joe"
val ageValue = 22 
run(query[Person].filter(p => p.name == lift(nameValue) && p.age > lift(ageValue))).string
// SELECT p.name, p.age FROM person p WHERE p.name = ? AND p.age > ?

It would be much more useful to use either the name of the case-class/tuple variable

SELECT p.name, p.age FROM person p WHERE p.name = ${name} AND p.age > ${age}

...or the variable name that is being used

SELECT p.name, p.age FROM person p WHERE p.name = ${nameValue} AND p.age > ${ageValue}

The former is a better solution but it is very hard to do because Quill only tracks lifted variables by position. The latter option is simpler because ScalarValueLift already has the variable name which of course does not work if it's a compound statement but we could detect such a situation and have a fallback.

@getquill/maintainers