Use ResizeImage in ColorScheme._imageProviderToScaled and remove timeout

[gawsfbet]

The timeout case should be handled by the caller of ColorScheme.fromImageProvider.

Note: the current impl where the listener is removed multiple times might result in the error Bad state: Stream has been disposed., as the stream attempts to remove the listener twice (once during image resolution and once when the timer expires)

List which issues are fixed by this PR. You must list at least one issue. An issue is not required if the PR fixes something trivial like a typo.
#124806

If you had to change anything in the flutter/tests repo, include a link to the migration guide as per the breaking change policy.

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
• I signed the CLA.
• I listed at least one issue that this PR fixes in the description above.
• 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.
• I followed the breaking change policy and added Data Driven Fixes where supported.
• All existing and new tests are passing.

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

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[Piinks]

Hey @gawsfbet can you sign the cla? This will likely need a test as well. Thank you for contributing!

[gawsfbet]

Hey @gawsfbet can you sign the cla? This will likely need a test as well. Thank you for contributing!

Already done it, thanks!

This PR mainly consists of refactoring a private method, and I have modified existing tests according to the new behavior. Do I need to write additional tests as well?

[QuncCccccc]

This PR mainly consists of refactoring a private method, and I have modified existing tests according to the new behavior. Do I need to write additional tests as well?

Thanks a lot for the contribution! Yes, if there are any new behaviors, please add unit tests to cover that:) Please let me know once this PR is ready to review! I saw it's still a draft, so not sure whether I should start reviewing😄