Move 'radixPrefix' from compiler modules to IDE modules

`radixPrefix` is used only in IDE now. So let's put it into IDE modules.

This commit is done in order to be able to use code dependent on
`radixPrefix` in `kotlin-ide` repo, because `kotlin-ide` depends on
1.4.0 artifacts of compiler. And `radixPrefix` isn't presented in
those artifacts

core/util.runtime/src/org/jetbrains/kotlin/utils/numbers.kt

@@ -23,11 +23,3 @@ fun extractRadix(value: String): NumberWithRadix = when {
     value.startsWith("0b") || value.startsWith("0B") -> NumberWithRadix(value.substring(2), 2)
     else -> NumberWithRadix(value, 10)
 }
-
-val NumberWithRadix.radixPrefix: String
-    get() = when (radix) {
-        2 -> "0b"
-        10 -> ""
-        16 -> "0x"
-        else -> error("Invalid radix for $this")
-    }

nj2k/src/org/jetbrains/kotlin/nj2k/conversions/ForConversion.kt

@@ -17,8 +17,8 @@ import org.jetbrains.kotlin.nj2k.tree.*
 import org.jetbrains.kotlin.nj2k.types.JKJavaArrayType
 import org.jetbrains.kotlin.nj2k.types.JKJavaPrimitiveType
 import org.jetbrains.kotlin.nj2k.types.JKNoType
+import org.jetbrains.kotlin.utils.NumberWithRadix
 import org.jetbrains.kotlin.utils.extractRadix
-import org.jetbrains.kotlin.utils.radixPrefix
 import kotlin.math.abs
 
 
@@ -231,6 +231,14 @@ class ForConversion(context: NewJ2kConverterContext) : RecursiveApplicableConver
         return "${numberWithRadix.radixPrefix}${fixedValue}"
     }
 
+    private val NumberWithRadix.radixPrefix: String
+        get() = when (radix) {
+            2 -> "0b"
+            10 -> ""
+            16 -> "0x"
+            else -> error("Invalid radix for $this")
+        }
+
     private fun indicesIterationRange(
         start: JKExpression,
         bound: JKExpression,