In #33705 we made it so that we generate pure functions for object/array literals in order to avoid having them be shared across elements/views. The problem this introduced is that further down the line the `ContantPool` uses the generated literal in order to figure out whether to share an existing factory or to create a new one. `ConstantPool` determines whether to share a factory by creating a key from the AST node and using it to look it up in the factory cache, however the key generation function didn't handle function invocations and replaced them with `null`. This means that the key for `{foo: pureFunction0(...)}` and `{foo: null}` are the same.
These changes rework the logic so that instead of generating a `null` key
for function invocations, we generate a variable called `<unknown>` which
shouldn't be able to collide with anything.
Fixes#35298.
PR Close#35481
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