The decorator downlevel transform is never used for actual class
decorators because Angular class decorators rely on immediate execution
for JIT. Initially we also supported downleveling of class decorators
for View Engine library output, but libraries are shipped using partial
compilation output and are not using this transform anymore.
The transform is exclusively used for JIT processing, commonly for
test files to help ease temporal dead-zone/forward-ref issues. We can
remove the class decorator downlevel logic to remove technical debt.
PR Close#49351
c241f63e8d