Update definition of downstream read/write.
Simplify equality of symbols by SID.
Revert "insertEffects: add an FScope to collection annotations"

This reverts commit bcad9fcc58bde7ab1d0f3c251891791bac5c0468.
Ensure that write-captures are not also read-captured.
Ensure that all lambdas can modify copy-captured closure.
Add equality of symbols to alias.
Fix hasRead/hasWrite to identify aliases, applications.
Fix has*InFunction to identify PSets.