[ci] Update version of Chromium in benchmarks to keep up with engine.

[ditman]

The oldest version of Chromium (84) we were using for benchmarking is no longer supported by the web engine, so we need to update to something newer than 87+.

This PR:

• Keeps the former "new" version as the new "old" version of Chromium (to have some sort of "continuity" in the benchmarks)
• Updates the "new" version to match the one used in flutter/engine.

This should allow web_benchmarks_test CHROMIUM_BUILD:XXX check to pass, and re-enable merges from master.

Closes: #3611

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/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 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.

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

[yjbanov]