Ensure transformFlags are correct before visiting a node.

[rbuckton]

When transforming a SpreadElementExpression in a CallExpression, we call createCallBinding which may return a new expression containing an existing subtree. However, this new expression has not had its transform flags computed. Then, when we go to visit the target, our visitor thinks there is nothing to do since no flags are set. To fix this, and catch any future instances of this issue, we will now call aggregateTransformFlags prior to visiting any node to ensure the flags are computed.

Fixes #12010

[rbuckton]

// CC: @mhegazy