Rewrite actual IntStack using class instead of typealias

If `IntStack` expanded to `IntArrayList`, it contains ambiguous actual functions: `push(int)` and `push(Integer)` (j2k interaction works a bit confused). K2 treats them as an error.

Unfortunately, fixing a third-party library with `IntArrayList` (fastutil) is rather complicated, especially considering the library uses code generation.

Fortunately, `IntStack` can be rewritten with just a class.

See also https://youtrack.jetbrains.com/issue/KT-66723

src/jvmMain/kotlin/CommonDefsImplJvm.kt

@@ -1,15 +1,21 @@
 package org.intellij.markdown.html
 
 import it.unimi.dsi.fastutil.ints.IntArrayList
-import it.unimi.dsi.fastutil.ints.IntStack
 import java.net.URLEncoder
-import java.util.Stack
 
 actual class BitSet actual constructor(size: Int): java.util.BitSet(size){
     actual val size = size()
 }
 
-actual typealias IntStack = IntArrayList
+actual class IntStack {
+    private val intArrayList = IntArrayList()
+
+    actual fun push(e: Int) = intArrayList.push(e)
+
+    actual fun pop(): Int = intArrayList.popInt()
+
+    actual fun isEmpty(): Boolean = intArrayList.isEmpty
+}
 
 private const val PUNCTUATION_MASK: Int = (1 shl Character.DASH_PUNCTUATION.toInt()) or
         (1 shl Character.START_PUNCTUATION.toInt())     or