[webview_flutter] Add an option to bypass SSL checks

[Colman]

When the webview encounters an SSL error, there is no option to be able to bypass the error. This PR implements a callback that gets called with the SSL error and certificate details. A decision can be returned to either ignore the error and proceed, or cancel the request.

https://github.com/flutter/flutter/issues/36925

Pre-launch Checklist

• [x] I read the Contributor Guide and followed the process outlined there for submitting PRs.
• [x] 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.)
• [x] I signed the CLA.
• [x] The title of the PR starts with the name of the package surrounded by square brackets, e.g. [shared_preferences]
• [x] I linked to at least one issue that this PR fixes in the description above.
• [x] I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy, or this PR is exempt from version changes.
• [x] I updated CHANGELOG.md to add a description of the change, following repository CHANGELOG style, or this PR is exempt from CHANGELOG changes.
• [x] 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.

[Colman]

I still have some tests to add, but I would like a first pass to check for bigger issues

[Colman]

Looks like webview_flutter_web (at least) doesn't have any significant changes and can be reverted?

Those changes are needed temporarily because this is a federated plugin. Please see: https://github.com/flutter/flutter/blob/master/docs/ecosystem/contributing/README.md#changing-federated-plugins

[bparrishMines]

This is blocked by the ProxyApi update for Android and iOS. https://github.com/flutter/packages/pull/7794 updates Android, and a similar PR for iOS will follow shortly.

[stuartmorgan-g]

from triage: iOS proxy updates are close to landing, at which point this will finally be unblocked.

[stuartmorgan-g]

@bparrishMines Can you take a look at updating this to the new wrapper?

[Piinks]

Greetings from stale PR triage, @stuartmorgan-g is this one still blocked?

[stuartmorgan-g]

No, it's unblocked now and needs to be updated to the new wrapper generator. @bparrishMines is planning on doing that, but has been on higher priority work. It should be pretty soon though.

[bparrishMines]

This PR doesn't allow me to edit so I took over this feature with: https://github.com/flutter/packages/pull/9150. Closing.