Make BigDecimalFromDigits FromDigits.Floating[BigDecimal]

The given instance in FromDigits for BigDecimal was incorrectly ignoring exponents in number literals,
This commit instead allows exponents in BigDecimal literals, and adds a test.

Author: bishabosha

library/src/scala/util/FromDigits.scala

@@ -158,7 +158,7 @@ object FromDigits {
     def fromDigits(digits: String, radix: Int): BigInt = BigInt(digits, radix)
   }
 
-  given BigDecimalFromDigits : FromDigits.Decimal[BigDecimal] {
+  given BigDecimalFromDigits : FromDigits.Floating[BigDecimal] {
     def fromDigits(digits: String): BigDecimal = BigDecimal(digits)
   }
 }

tests/run/genericNumLits.check

@@ -1,5 +1,7 @@
 13232202002020202020202
 -50390822187678765893036
 132322020020.223
+1.00000000000000001234E+239
+1.00000000000000001234E-203
 Even(1234)
 malformed

tests/run/genericNumLits.scala

@@ -4,6 +4,8 @@ object Test extends App {
   val x: BigInt = 13232202002020202020202
   val y: BigInt = -0xaabb12345ACF12345AC
   val z: BigDecimal = 132322020020.223
+  val w: BigDecimal = 10000000000000000.1234e223
+  val q: BigDecimal = 100000000000000001234e-223
 
   case class Even(n: Int)
 
@@ -20,6 +22,8 @@ object Test extends App {
   println(x)
   println(y)
   println(z)
+  println(w)
+  println(q)
   println(e)
 
   try println(123: Even)
@@ -45,6 +49,18 @@ object Test extends App {
   (z: Any) match {
     case 132_322_020_020.223: BigDecimal => ()
   }
+  w match {
+    case 10000000000000000.1234e223 => ()
+  }
+  (w: Any) match {
+    case 10_000_000_000_000_000.1234e223: BigDecimal => ()
+  }
+  q match {
+    case 100000000000000001234e-223 => ()
+  }
+  (q: Any) match {
+    case 100_000_000_000_000_001_234e-223: BigDecimal => ()
+  }
 
   e match {
     case 1234 =>
@@ -54,4 +70,4 @@ object Test extends App {
     case 1234: Even =>
     case _: Even =>
   }
-}
+}