[compiler] Fix Symbol shadowing in generated code

[kenanAST]

Summary

Fixes #35379

When a component is named Symbol, it shadows the global Symbol object. The compiler currently emits Symbol.for("react.memo_cache_sentinel") for memoization checks, which breaks at runtime because it tries to call .for() on the React component instead of the global Symbol.

This changes the codegen to use globalThis.Symbol.for() instead, which works regardless of local shadowing. The same fix is applied to the runtime package.

How did you test this change?

Updated the test fixtures to verify the new output format. The generated code now uses:

if ($[0] === globalThis.Symbol.for("react.memo_cache_sentinel")) {

This matches the approach used in Babel's own codebase (see babel/babel#3250) where they had the same shadowing issue.

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