Add simplified overloads of String<->ByteArray/CharArray conversions

These overloads cover the most common cases of conversion of the entire
String or Byte/CharArray, avoiding extra index check and branching.

#KT-24810, KT-29265

libraries/stdlib/common/src/kotlin/TextH.kt

@@ -116,6 +116,13 @@ public expect fun String(chars: CharArray): String
 @SinceKotlin("1.2")
 public expect fun String(chars: CharArray, offset: Int, length: Int): String
 
+/**
+ * Concatenates characters in this [CharArray] into a String.
+ */
+@SinceKotlin("1.3")
+@ExperimentalStdlibApi
+public expect fun CharArray.concatToString(): String
+
 /**
  * Concatenates characters in this [CharArray] or its subrange into a String.
  *
@@ -129,6 +136,13 @@ public expect fun String(chars: CharArray, offset: Int, length: Int): String
 @ExperimentalStdlibApi
 public expect fun CharArray.concatToString(startIndex: Int = 0, endIndex: Int = this.size): String
 
+/**
+ * Returns a [CharArray] containing characters of this string.
+ */
+@SinceKotlin("1.3")
+@ExperimentalStdlibApi
+public expect fun String.toCharArray(): CharArray
+
 /**
  * Returns a [CharArray] containing characters of this string or its substring.
  *
@@ -142,6 +156,15 @@ public expect fun CharArray.concatToString(startIndex: Int = 0, endIndex: Int =
 @ExperimentalStdlibApi
 public expect fun String.toCharArray(startIndex: Int = 0, endIndex: Int = this.length): CharArray
 
+/**
+ * Decodes a string from the bytes in UTF-8 encoding in this array.
+ *
+ * Malformed byte sequences are replaced by the replacement char `\uFFFD`.
+ */
+@SinceKotlin("1.3")
+@ExperimentalStdlibApi
+public expect fun ByteArray.decodeToString(): String
+
 /**
  * Decodes a string from the bytes in UTF-8 encoding in this array or its subrange.
  *
@@ -161,6 +184,15 @@ public expect fun ByteArray.decodeToString(
     throwOnInvalidSequence: Boolean = false
 ): String
 
+/**
+ * Encodes this string to an array of bytes in UTF-8 encoding.
+ *
+ * Any malformed char sequence is replaced by the replacement byte sequence.
+ */
+@SinceKotlin("1.3")
+@ExperimentalStdlibApi
+public expect fun String.encodeToByteArray(): ByteArray
+
 /**
  * Encodes this string or its substring to an array of bytes in UTF-8 encoding.
  *