Fix the NNC-disabled path in static runtime for perf comparisons
Summary:
The path which has NNC/LLVM disabled still constructs a tensor
expression, even though `supports()` will always return false, so a
`KernelScope` is necessary to manage those memory allocations.
I guess we could avoid building the TEs at all in this case, but it's pretty
clean this way.
Test Plan:
```
scripts/bertrand/static_runtime/run.sh
```
Reviewed By: hlu1
Differential Revision: D29415909
fbshipit-source-id: dde43de8516b9a2cf9f5f7f3699962bf9ccd8c30
