Drop Progression<T> and its deprecated properties: start, end, increment.

Drop deprecated range extensions.
Make progression constructors private.

libraries/stdlib/test/language/RangeIterationTest.kt

@@ -31,12 +31,6 @@ public open class RangeIterationTestBase {
                 last = sequence.last
                 increment = sequence.step
             }
-            // TODO: Drop this branch
-            is Progression -> {
-                first = sequence.start
-                last = sequence.end
-                increment = sequence.increment
-            }
             else -> throw IllegalArgumentException("Unsupported sequence type: $sequence")
         }
 

libraries/stdlib/test/language/RangeJVMTest.kt

@@ -1,6 +1,7 @@
 @file: Suppress("DEPRECATION_ERROR")
 package language
 
+import kotlin.ranges.LongProgression.Companion
 import java.lang.Double as jDouble
 import java.lang.Float as jFloat
 import org.junit.Test as test
@@ -26,9 +27,9 @@ public class RangeJVMTest {
     @test fun illegalProgressionCreation() {
         fun assertFailsWithIllegalArgument(f: () -> Unit) = assertFailsWith(IllegalArgumentException::class, block = f)
         // create Progression explicitly with increment = 0
-        assertFailsWithIllegalArgument { IntProgression(0, 5, 0) }
-        assertFailsWithIllegalArgument { LongProgression(0, 5, 0) }
-        assertFailsWithIllegalArgument { CharProgression('a', 'z', 0) }
+        assertFailsWithIllegalArgument { IntProgression.fromClosedRange(0, 5, 0) }
+        assertFailsWithIllegalArgument { LongProgression.fromClosedRange(0, 5, 0) }
+        assertFailsWithIllegalArgument { CharProgression.fromClosedRange('a', 'z', 0) }
 
 
         assertFailsWithIllegalArgument { 0..5 step 0 }