Pull in main branch into v4_webview

[bparrishMines]

Pulls the main branch into the v4_webview branch. This is for work being done for flutter/flutter#94051.

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 relevant style guides and ran the auto-formatter. (Unlike the flutter/flutter repo, the flutter/plugins repo does use dart format.)
• I signed the CLA.
• The title of the PR starts with the name of the plugin surrounded by square brackets, e.g. [shared_preferences]
• I listed 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.
• 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.

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[ditman]

Note: this branch is duplicating commit hashes from main into it, and may cause "redness" in the tree, because of the way github <-> cirrus talk to each other. Are we vending two versions of the webview from this repo?

[stuartmorgan-g]

RSLGTM once the pub get resolving failures are addressed.

[stuartmorgan-g]

Are we vending two versions of the webview from this repo?

We're developing the new v4 interface in parallel with the current interface, but made some tactical mistakes in the development and ended up in a situation where iterating the v4 interface would actually require a major version change (because we started building the new implementations in-tree before finding issues in the interface). To avoid that, we're finishing v4 in a branch, and then will do a single breaking change to adopt v4 as the new interface once we have things working end to end on the branch.