[web] - fix text editing IME composition interruption on geometry updates

[htoor3]

This change fixes an issue where IME composition gets interrupted when the setEditableSizeAndTransform platform message is received mid-composition. This occurs when a multiline input expands and needs to inform the underlying textarea to update its size.

Fixes https://github.com/flutter/flutter/issues/134797 Fixes https://github.com/flutter/flutter/issues/98817

Pre-launch Checklist

• [x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
• [x] I read the [Tree Hygiene] wiki page, which explains my responsibilities.
• [x] I read and followed the [Flutter Style Guide] and the [C++, Objective-C, Java style guides].
• [x] I listed at least one issue that this PR fixes in the description above.
• [x] I added new tests to check the change I am making or feature I am adding, or the PR is [test-exempt]. See [testing the engine] for instructions on writing and running engine tests.
• [x] I updated/added relevant documentation (doc comments with ///).
• [x] I signed the [CLA].
• [ ] All existing and new tests are passing.