Optimize MetalRedrawer synchronization

[ASalavei]

Note: The change has been already reviewer in another MR, but failed to merge because of the merging issues.

Remove inflightSemaphore because does not prevent from awaiting the main thread on the nextDrawable().
Replace InflightCommandBuffers and replace it with the Dispatch Group.

Fixes https://youtrack.jetbrains.com/issue/CMP-9494/Optimize-MetalRedrawer-synchronization

Release Notes

N/A

[ASalavei]

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Result: Code Review for MetalRedrawer Synchronization Optimization
The pull request "Optimize MetalRedrawer synchronization" was reviewed. The review identified a potential race condition in the synchronization logic when the application transitions to the background and an outdated variable name and description in a comment.

⚠️ 2 issues found

1. compose/ui/ui/src/iosMain/kotlin/androidx/compose/ui/window/MetalRedrawer.ios.kt : 235
   When the application moves to the background, dispatch_group_wait is used to wait for in-flight command buffers. However, dispatch_group_enter is called inside encodeAndPresentBlock, which may be dispatched asynchronously to the renderingDispatchQueue. If the block has been dispatched but not yet started execution, the inflightCommandBuffersGroup will be empty, and dispatch_group_wait will return immediately. This creates a race condition where GPU work can be committed after the application has transitioned to the background, potentially violating Metal's background execution rules.

2. compose/ui/ui/src/iosMain/kotlin/androidx/compose/ui/window/MetalRedrawer.ios.kt : 232
   The comment refers to inflightCommandBuffers, which is the name of the variable that was removed in this PR. It should be updated to inflightCommandBuffersGroup. Additionally, the comment says "synchronously schedule", but the code actually waits for the command buffers to complete. A more accurate description would be "synchronously wait for all in-flight command buffers to complete".