isPressed

Fix crash when we press right mouse button during dragging with left button

Fixes JetBrains/compose-multiplatform#1426
Fixes JetBrains/compose-multiplatform#1176

Fixes JetBrains/compose-multiplatform#1430

Get rid of mousePressed from ComposeScene

mousePressed is unreliable on Windows (we can miss the release event), and doesn't work well with multiple buttons.

After this fix, mouseClickable only reacts to the first pressed button. Right button click doesn't trigger callback, if there is already left mouse button is pressed.

`Clickable` shouldn't be able to handle these cases. If users would want simultaneously handle multiple buttons, they have to use low-level api:
```
Modifier.pointerInput(Unit) {
    while (true) {
        val event = awaitPointerEventScope { awaitPointerEvent() }

        if (event.type == PointerEventType.Press && event.buttons.isPrimaryPressed) {
            // do something
        } else if (event.type == PointerEventType.Press && event.buttons.isSecondaryPressed) {
            // do something
        }
    }
}
```
(it is verbose, there is a field for improvement)

Test: ./gradlew jvmTest desktopTest -Pandroidx.compose.multiplatformEnabled=true
Test: the snippet from JetBrains/compose-multiplatform#1149, because changed the code for that fix

Remove pointerId from ComposeScene

pointerId was indroduced in https://android-review.googlesource.com/c/platform/frameworks/support/+/1402607, because double click didn't work (see https://jetbrains.slack.com/archives/GT449QBCK/p1597328095373000)

But it messes with hover and clicking multiple mouse buttons at the same time.

Double clicking still works after removing it:
```
import androidx.compose.foundation.ExperimentalFoundationApi
import androidx.compose.foundation.background
import androidx.compose.foundation.combinedClickable
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.size
import androidx.compose.ui.Modifier
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.unit.dp
import androidx.compose.ui.window.singleWindowApplication

@OptIn(ExperimentalFoundationApi::class)
fun main() = singleWindowApplication {
    Box(
        Modifier
        .size(300.dp)
        .background(Color.Red)
            .combinedClickable(onDoubleClick = {
                println("onDoubleClick")
            }, onClick = {
                println("onClick")
            })
    ) {
    }
}
```

Fixes JetBrains/compose-multiplatform#1176

Test: ./gradlew jvmTest desktopTest -Pandroidx.compose.multiplatformEnabled=true
Test: manual (see the snippet)

compose/ui/ui/src/desktopMain/kotlin/androidx/compose/ui/ComposeScene.desktop.kt

@@ -23,6 +23,7 @@ import androidx.compose.ui.input.pointer.PointerInputEvent
 import androidx.compose.ui.input.pointer.PointerInputEventData
 import androidx.compose.ui.input.pointer.PointerKeyboardModifiers
 import androidx.compose.ui.input.pointer.PointerType
+import androidx.compose.ui.input.pointer.areAnyPressed
 import androidx.compose.ui.platform.AccessibilityController
 import androidx.compose.ui.platform.AccessibilityControllerImpl
 import androidx.compose.ui.platform.PlatformComponent
@@ -52,7 +53,6 @@ internal actual fun pointerInputEvent(
     timeMillis: Long,
     nativeEvent: Any?,
     type: PointerType,
-    isMousePressed: Boolean,
     pointerId: Long,
     scrollDelta: Offset,
     buttons: PointerButtons,
@@ -67,7 +67,7 @@ internal actual fun pointerInputEvent(
                 timeMillis,
                 position,
                 position,
-                isMousePressed,
+                buttons.areAnyPressed,
                 type,
                 scrollDelta = scrollDelta
             )

compose/ui/ui/src/skikoMain/kotlin/androidx/compose/ui/ComposeScene.skiko.kt

@@ -140,9 +140,6 @@ class ComposeScene internal constructor(
 
     private val defaultPointerStateTracker = DefaultPointerStateTracker()
 
-    private var pointerId = 0L
-    private var isMousePressed = false
-
     private val job = Job()
     private val coroutineScope = CoroutineScope(coroutineContext + job)
     // We use FlushCoroutineDispatcher for effectDispatcher not because we need `flush` for
@@ -390,22 +387,18 @@ class ComposeScene internal constructor(
         val actualButtons = buttons ?: defaultPointerStateTracker.buttons
         val actualKeyboardModifiers = keyboardModifiers ?: defaultPointerStateTracker.keyboardModifiers
 
-        when (eventType) {
-            PointerEventType.Press -> isMousePressed = true
-            PointerEventType.Release -> isMousePressed = false
-        }
         val event = pointerInputEvent(
             eventType,
             position,
             timeMillis,
             nativeEvent,
             type,
-            isMousePressed,
-            pointerId,
+            pointerId = 0,
             scrollDelta,
             actualButtons,
             actualKeyboardModifiers
         )
+
         when (eventType) {
             PointerEventType.Press -> onMousePressed(event)
             PointerEventType.Release -> onMouseReleased(event)
@@ -435,7 +428,6 @@ class ComposeScene internal constructor(
     private fun onMouseReleased(event: PointerInputEvent) {
         val owner = hoveredOwner ?: focusedOwner
         owner?.processPointerInput(event)
-        pointerId += 1
     }
 
     private var pointLocation = Offset.Zero
@@ -474,7 +466,6 @@ internal expect fun pointerInputEvent(
     timeMillis: Long,
     nativeEvent: Any?,
     type: PointerType,
-    isMousePressed: Boolean,
     pointerId: Long,
     scrollDelta: Offset,
     buttons: PointerButtons,