[WIP] [android_camera_camerax] Fix incorrect camera mirroring for front cameras on devices using ImageReader Impeller backend

[camsim99]

Fixes the incorrect camera mirroring when the front camera is used on devices that use the ImageReader Impeller backend. TLDR: for relevant rotated preview implementation, when the front camera is used, mirror the camera preview across the y-axis when the device is in a portrait orientation or across the x-axis when the device is in a landscape orientation.

Fixes flutter/flutter#156974.

cc @jesswrd, co-author of this PR

Pre-Review Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene page, which explains my responsibilities.
• 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.

If you need help, consider asking for advice on the #hackers-new channel on Discord.

Footnotes

1. Regular contributors who have demonstrated familiarity with the repository guidelines only need to comment if the PR is not auto-exempted by repo tooling. ↩ ↩² ↩³