[camera] Remove OCMock from AvailableCamerasTests, CameraOrientationTests and ThreadSafeEventChannelTests

[mchudy]

Follow-up on #8342. This should be merged after #8351

• Removes OCMock dependency in AvailableCamerasTests.m, CameraOrientationTests.m and ThreadSafeEventChannelTests.m
• Introduces new protocol wrappers to enable mocking FLTEventChannel and FLTCameraDeviceDiscovering

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• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy, or this PR is exempt from version changes.
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[hellohuanlin]

I haven't seen 2 released in a single PR before. This is probably not a standard practice (@stuartmorgan will know)

May worth splitting into 2 PRs, which can make the review easier/faster.

[stuartmorgan]

CI won't allow this; it can either be two PRs, or it can be one PR with a single version bump.

[mchudy]

So this PR was meant to be merged after #8351 (it includes changes from that PR), that's why there are two new versions. So either we merge them one after the other or we close #8351 and only merge this one. Sorry for making it confusing.

[hellohuanlin]

There's a trick that you can set base branch your previous branch first, and after that gets landed, change the base branch back to main.

[mchudy]

Good idea, but I believe that I can only set the base branch as a branch that exists in the main repo, it doesn't list branches from my fork

[hellohuanlin]

oh i will review after the previous PR is in then. otherwise it's hard to tell which part is new change.

[hellohuanlin]

I'd just call the protocol FLTCaptureDevice since it's a noun (rather than a capability), as discussed in the design doc

[mchudy]

Done