dillon1000/react

Remove unnecessary scopes for value blocks

The example earlier in the stack had unreachable code in the output because 
there was an unnecessary memoization block around an assignment. This was a 
holdover from before we moved the logic to expand mutable ranges for phis from 
LeaveSSA to InferMutableRanges. We were conservatively assigning a mutable range 
to all variables with a phi, even those that didn't strictly need one. 

Removing the range extension logic in LeaveSSA fixed the issue, but uncovered 
the fact that AlignReactiveScopesToBlockScopes was missing a case to handle 
optionals. 

## Test Plan 

Synced internally and ran a snapshot/comparison of compilation before/after 
(P1197734337 for those curious). The majority of components get fewer memo slots 
thanks to not needing to memoize non-allocating value block expressions like 
ternaries/optionals. In a few cases, the fact that we're no longer assigning a 
mutable range for value blocks (unless there is actually a mutation!) means we 
get more fine-grained memoization and increase the number of memoization blocks. 
So overall this appears to be correct, improve memoization, and reduce code 
size.