[camera_android_camerax] Allow usage of all use cases concurrently

[camsim99]

Removes guardrails to avoid previously unsupported concurrent camera use cases (this was changed in a later version of CameraX that came after the guards were implemented. See #6608 for details). Fixes flutter/flutter#150387.

As a bonus, also fixes flutter/flutter#157181 by:

1. Using delayed Futures instead of calls to sleep which I theorize was blocking calls happening on the native side, so the sleep calls were not actually giving time for the camera to initialize
2. Ensuring all calls to start video recording have a delay afterwards to, again, give time for the camera to initialize.

I tracked down these fixes by noticing we actually are not surfacing video recording errors; we actually were getting the ERROR_NO_VALID_DATA error. Filed an issue to expose all video recording errors like this for easier debugging in the future: flutter/flutter#182960.

Pre-Review Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
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• I read and followed the relevant style guides and ran the auto-formatter.
• I signed the CLA.
• The title of the PR starts with the name of the package surrounded by square brackets, e.g. [shared_preferences]
• I linked to at least one issue that this PR fixes in the description above.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy, or I have commented below to indicate which version change exemption this PR falls under¹.
• I updated CHANGELOG.md to add a description of the change, following repository CHANGELOG style, or I have commented below to indicate which CHANGELOG exemption this PR falls under¹.
• I updated/added any relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or I have commented below to indicate which test exemption this PR falls under¹.
• All existing and new tests are passing.

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[gemini-code-assist]

Code Review

This pull request correctly removes obsolete logic that prevented concurrent use of camera features like video recording, preview, and image analysis/capture. This simplification is made possible by updates in the underlying CameraX library, which now supports these concurrent operations. The changes primarily involve deleting hardware-level check code from startVideoCapturing in android_camera_camerax.dart and removing the corresponding tests that verified the old, restrictive behavior. The pubspec.yaml and CHANGELOG.md have also been updated to reflect these changes. The pull request improves code maintainability by removing unnecessary complexity.

[gemini-code-assist]

Code Review

This pull request removes outdated restrictions on concurrent camera use cases, which simplifies the codebase and enables more flexible camera functionality. It also fixes an issue in the integration tests where video recording could fail by replacing blocking sleep calls with non-blocking Future.delayed, which is a great improvement for test stability. The corresponding documentation and tests have been updated to reflect these changes. I have one suggestion to make the changelog more comprehensive.

[gemini-code-assist]

This is a great summary of the main change! To make the changelog even more helpful for users, consider also mentioning the fix for the video recording issue (#157181). The repository's CHANGELOG style guide also recommends linking to the fixed issues.

How about something like this?

Suggested change

	* Removes outdated restrictions against concurrent camera use cases.
	* Removes outdated restrictions against concurrent camera use cases (fixes flutter/flutter#150387).
	* Fixes an issue where video recording could fail immediately after starting on some devices (fixes flutter/flutter#157181).

References

1. The repository's CHANGELOG style guide recommends that if a change fixes one or more issues, they should be listed at the end of the description in parentheses. This change also includes a significant bug fix that would be valuable to mention for users. ^(link)