[camera] Add support for zero-shutter-lag capture

[toyaji]

Combines the interface and both implementations in one PR per the federated plugin process; splits into an interface-first PR once the direction is approved. The API shape is a proposal for flutter/flutter#190598 — happy to reshape it however you prefer.

Adds explicit zero-shutter-lag control: an opt-in on Android, where the default capture mode leaves it off, and an opt-out on iOS, where the OS enables it automatically when the session supports it.

What's added

camera_platform_interface — two methods on CameraPlatform, modeled on the existing setJpegImageQuality / getSupportedVideoStabilizationModes patterns. Defaults are false / no-op, so nothing changes for platforms or apps that don't opt in:

Future<bool> isZeroShutterLagSupported(int cameraId);
Future<void> setZeroShutterLagEnabled(int cameraId, bool enabled);

camera_android_camerax — CameraInfo.isZslSupported() and ImageCapture.Builder.setCaptureMode(CAPTURE_MODE_ZERO_SHUTTER_LAG). The capture mode is construction-only, so the use case is recreated — the approach setJpegImageQuality already uses for the same constraint, now sharing one helper so the two settings can't drop each other.

camera_avfoundation — isZeroShutterLagSupported / isZeroShutterLagEnabled (iOS 17+). Enabling is guarded on the support query (setting it while unsupported throws NSInvalidArgumentException) and wrapped in beginConfiguration/commitConfiguration. The requested state is reapplied after camera switches, which silently reset it. Apps that never call the setter are left untouched, so iOS keeps its automatic behavior on upgrade.

Notes for reviewers

• Platform defaults differ: Android leaves ZSL off by default, iOS 17+ turns it on automatically when supported — so the same call is an opt-in on Android and an opt-out on iOS. Measurements below.
• Experimental API: CAPTURE_MODE_ZERO_SHUTTER_LAG is @ExperimentalZeroShutterLag, handled with per-declaration @OptIn like this plugin's existing ExperimentalCamera2Interop / ExperimentalLensFacing / ExperimentalPersistentRecording. gradlew lint is clean.
• Unsupported cases need no app handling: CameraX falls back on its own; iOS is guarded by the support query.
• Generated files: regenerating with pigeon 26.1.5 also reverts two pre-existing hand-edits from [camera_android, camera_android_camerax, camera_avfoundation] Add setJpegImageQuality #11616 (a redundant Int32 cast and a missing doc comment).
• CI: the publish check is red by design — the last commit holds the make-deps-path-based overrides and is reverted before landing.

On-device measurements

Android — Galaxy S21 (SM-G991N), 5 captures per mode, shutter fired via adb shell input tap. A running millisecond stopwatch was photographed; the time visible in each saved photo shows how far behind the shutter tap the captured frame is.

	Captured frame	Shutter → file saved
MINIMIZE_LATENCY (current)	baseline	912 ms
ZERO_SHUTTER_LAG	629 ms earlier	639 ms

iOS — iPhone (iOS 26.5), ResolutionPreset.max, 5 captures per mode after discarding one warm-up capture. Compares AVCapturePhoto.timestamp against the host-clock time of the capturePhoto call, so a negative value means the saved frame predates the call.

	Frame vs. shutter call	Shutter → delegate
ZSL off	+279 ms	941 ms
ZSL on	−74 ms	689 ms

With ZSL on, every captured frame predated the capture call. Support is session-dependent rather than device-wide: the same device reports supported at ResolutionPreset.max and unsupported at medium.

Since iOS enables this automatically, these numbers describe what the toggle controls — not an improvement this PR delivers on iOS.

Part of flutter/flutter#190598

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[gemini-code-assist]

Code Review

This pull request adds support for zero-shutter-lag still image capture to the Flutter camera plugin. It introduces isZeroShutterLagSupported and setZeroShutterLagEnabled to the camera_platform_interface and implements them in the Android (CameraX) and iOS (AVFoundation) implementations, along with corresponding tests and Pigeon updates. Feedback on the changes suggests awaiting the asynchronous isZslSupported call in the Android implementation to avoid potential static analysis errors.