Make synced react-is version more obvious

[eps1lon]

We treated react-is separately in a separate task but it really should be handled the same as React, ReactDOM etc.

It is still missing a vendored version of the experimental release channel. We only use isValidElementType though and that method needs to move to the renderer anyway. I'd rather prioritize the renderer work instead of more aliasing effort in our bundler.

Test plan

-pushd packages/next && rm -rf src/compiled/react-is && pnpm taskr copy_vendor_react will leave everything as-is

[eps1lon]

• #67192
• #66711
• #67189 👈
• canary

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[ijjk]

Tests Passed