Weird mapper inconsistency based on how the json is created

[BenFradet]

I have noticed a weird inconsistency depending on how the json is created when interacting with the mapper (c.f. #48):

import cats.syntax.either._
import cats.syntax.eq._
import io.circe.Json
import io.circe.literal._
import io.circe.syntax._

val json1 = json"""{"latitude": 43.1, "longitude": 32.1}""" // same with im.circe.parser.parse
val json2 = Json.obj("latitude" := Json.fromDoubleOrNull(43.1), "longitude" := Json.fromDoubleOrNull(32.1))

println(json1 === json2) // true

// a lib I'm using requires me to convert it to an object
val pojo1 = io.circe.jackson.mapper.convertValue(json1, classOf[Object])
val pojo2 = io.circe.jackson.mapper.convertValue(json2, classOf[Object])

println(pojo1 == pojo2) // false

// String
val c1 = Either.catchNonFatal(
  pojo1.asInstanceOf[java.util.HashMap[Object, Object]].get("latitude").getClass)
// Double
val c2 = Either.catchNonFatal(
  pojo2.asInstanceOf[java.util.HashMap[Object, Object]].get("latitude").getClass)

println(c1)
println(c2)

using circe-literal or parse doubles get turned to strings whereas they stay doubles when creating jsons in line.

Here is a scastie reproducing the issue https://scastie.scala-lang.org/VMydlc7ITW2PYBn2NgizUw . However it relies on #48.