WASM: Implement wasm-native strings part 1

There are several changes here but they all required for at least one test to pass.
- Implemented String class and several utility functions using built-in CharArray
- Added new constant memory segment to hold string literals and required funcs to work with them
- Added very crude mostly incorrect rudimentary ability to pass strings back to javascript

libraries/stdlib/wasm/src/kotlin/Text.kt

@@ -287,7 +287,7 @@ public actual fun CharArray.concatToString(startIndex: Int, endIndex: Int): Stri
  */
 @SinceKotlin("1.3")
 @ExperimentalStdlibApi
-public actual fun String.toCharArray(): CharArray = TODO("Wasm stdlib: Text")
+public actual fun String.toCharArray(): CharArray = this.chars
 
 /**
  * Returns a [CharArray] containing characters of this string or its substring.