[JIT] Introduce a fake Tensor creation node for IR unit tests (#34334)
Summary:
**Summary**
There is often a need to create a Tensor when writing IR by hand for JIT
optimisation pass unit tests. The only options for this today are real
Tensor creation functions like `aten::ones`. Any test that uses these functions
must also use the same default arguments as the Python/C++ API, which means
that all of the tests have to be updated when the API is updated. This commit
introduces a new primitive, `prim::MakeTestTensor` with schema `() -> Tensor` that
should be used in unit tests instead of real Tensor creation functions. This new
primitive has no public-facing API, so the maintenance burden is much lower.
**Testing**
This commit updates the alias analysis and DCE tests to use `prim::MakeTestTensor` instead of
`aten::rand`, `aten::ones`, and `aten::zeros`.
```
$ ./bin/test_jit
CUDA not available. Disabling CUDA and MultiCUDA tests
Note: Google Test filter = *-*_CUDA:*_MultiCUDA
[==========] Running 75 tests from 1 test case.
[----------] Global test environment set-up.
[----------] 75 tests from JitTest
[ RUN ] JitTest.ADFormulas
[ OK ] JitTest.ADFormulas (82 ms)
[ RUN ] JitTest.Attributes
[ OK ] JitTest.Attributes (0 ms)
...
...
...
[ RUN ] JitTest.LiteInterpreterPrim
[ OK ] JitTest.LiteInterpreterPrim (0 ms)
[ RUN ] JitTest.LiteInterpreterLoadOrigJit
[ OK ] JitTest.LiteInterpreterLoadOrigJit (2 ms)
[----------] 75 tests from JitTest (150 ms total)
[----------] Global test environment tear-down
[==========] 75 tests from 1 test case ran. (150 ms total)
[ PASSED ] 75 tests.
```
**Fixes**
This pull request fixes https://github.com/pytorch/pytorch/issues/33500.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/34334
Differential Revision: D20296437
Pulled By: SplitInfinity
fbshipit-source-id: df4e7b0881ae4913424e5a409bfa171a61c3e568
