compiler: Use types to decide which scopes are eligible for merging

In MergeReactiveScopesThatInvalidateTogether when deciding which scopes were eligible for mergin at all, we looked specifically at the instructions whose lvalue produces the declaration. So if a scope declaration was `t0`, we'd love for the instruction where `t0` was the lvalue and look at the instruction type to decide if it is eligible for merging.

Here, we use the inferred type instead (now that the inferred types support the same set of types of instructions we looked at before). This allows us to find more cases where scopes can be merged.

ghstack-source-id: 0e3e05f24ea0ac6e3c43046bc3e114f906747a04
Pull Request resolved: https://github.com/facebook/react/pull/29157