Fix crash in CircularProgressIndicator when switching themes (#360)

Fixes #359 by making sure we only have one source of truth when it comes
to the number of frames in the indicator.

Having the frame count as a separate state might lead to unfortunate
race conditions, where the frames array has changed but the count hasn't
yet, causing index out of bounds error. Now, the frames count is only
computed when needed, synchronously, in the composition.

I have been furiously switching themes for over a minute and can't make
the component crash anymore.

ui/src/main/kotlin/org/jetbrains/jewel/ui/component/CircularProgressIndicator.kt

@@ -13,9 +13,7 @@ import androidx.compose.runtime.Composable
 import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateListOf
-import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
-import androidx.compose.runtime.setValue
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.graphics.painter.Painter
@@ -76,7 +74,6 @@ private fun CircularProgressIndicatorImpl(
 ) {
     val defaultColor = if (JewelTheme.isDark) Color(0xFF6F737A) else Color(0xFFA8ADBD)
     val frames = remember { mutableStateListOf<Painter>() }
-    var framesCount by remember { mutableStateOf(0) }
 
     val density = LocalDensity.current
     LaunchedEffect(density, style.color, defaultColor) {
@@ -87,13 +84,13 @@ private fun CircularProgressIndicatorImpl(
                     loadSvgPainter(it.byteInputStream(), density)
                 },
             )
-            framesCount = frames.size
         }
     }
 
-    if (framesCount == 0) {
+    if (frames.isEmpty()) {
         Box(modifier.size(iconSize))
     } else {
+        val framesCount = frames.size
         val transition = rememberInfiniteTransition("CircularProgressIndicator")
         val currentIndex by
             transition.animateValue(