[camera_web] Don't require enumerating cameras on web

[QoLTech]

Enumerating available cameras on web requires permission and activates hardware. This PR allows initializing the camera controller without having to enumerate available cameras first.

flutter/flutter#145541

Continues where #6369 left off

Pre-launch 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. (Unlike the flutter/flutter repo, the flutter/packages repo does use dart format.)
• 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 this PR is [exempt from version changes].
• I updated CHANGELOG.md to add a description of the change, [following repository CHANGELOG style], or this PR is [exempt from CHANGELOG changes].
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is [test-exempt].
• All existing and new tests are passing.

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

[ditman]

The CLA has been signed, I'm marking the google-cla bot comment above as "resolved".

[QoLTech]

I am stuck here - I'm not sure how to dive into the tests to see exactly what is failing. Can anyone help me out here?

[bparrishMines]

@QoLTech You should be able to click on Details -> View more details on flutter-dashboard -> stdout [raw]. Let me know if this works for you.

It looks like one of the tests in example/integration_test/camera_test.dart is failing in the plugin:

Failure Details:
Failure in method: returns a lens direction based on the first video track settings
══╡ EXCEPTION CAUGHT BY FLUTTER TEST FRAMEWORK ╞═════════════════
The following StateError was thrown running a test:
Bad state: No method stub was called from within `when()`. Was a
real method called, or perhaps an extension method?

When the exception was thrown, this was the stack:
dart-sdk/lib/_internal/js_dev_runtime/private/ddc_runtime/errors.dart 307:3  throw_
package:mocktail/src/mocktail.dart.js 274:19                                 [_completeWhen]
package:mocktail/src/mocktail.dart.js 261:33                                 thenReturn
camera_test.dart.js 1639:384                                                 <fn>
dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 622:19          <fn>
dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 647:23          <fn>
dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 541:3           _asyncStartSync
camera_test.dart.js 1645:24                                                  <fn>
package:flutter_test/src/test_text_input_key_handler.dart.js 12373:44        <fn>
dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 622:19          <fn>
dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 647:23          <fn>
dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 593:31          <fn>
dart-sdk/lib/async/zone.dart 1538:47                                         _rootRunUnary
dart-sdk/lib/async/zone.dart 1429:19                                         runUnary
dart-sdk/lib/async/future_impl.dart 208:18                                   handleValue
dart-sdk/lib/async/future_impl.dart 932:44                                   handleValueCallback
dart-sdk/lib/async/future_impl.dart 961:13                                   _propagateToListeners
dart-sdk/lib/async/future_impl.dart 712:5                                    [_completeWithValue]
dart-sdk/lib/async/future_impl.dart 792:7                                    <fn>
dart-sdk/lib/async/zone.dart 1525:13                                         _rootRun
dart-sdk/lib/async/zone.dart 1422:19                                         run
dart-sdk/lib/async/zone.dart 1321:7                                          runGuarded
dart-sdk/lib/async/zone.dart 1362:23                                         callback
dart-sdk/lib/async/schedule_microtask.dart 40:11                             _microtaskLoop
dart-sdk/lib/async/schedule_microtask.dart 49:5                              _startMicrotaskLoop
dart-sdk/lib/_internal/js_dev_runtime/patch/async_patch.dart 186:7           <fn>

The test description was:
  returns a lens direction based on the first video track
  settings

[stuartmorgan-g]

From triage: @QoLTech Are you still planning on updating this PR to address the test failures discussed above?