Add a test to measure `import torch` time (#56041)
Summary:
This PR adds a couple very simple tests which (as the code comment says) measure the time it takes to `import torch` and ask for the CUDA device count.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/56041
Test Plan:
```
$ rm -r /tmp/reports ; python3 test/test_import_time.py --save-xml=/tmp/reports
Running tests...
----------------------------------------------------------------------
..
----------------------------------------------------------------------
Ran 2 tests in 1.855s
OK
Generating XML reports...
```
```
$ tools/print_test_stats.py /tmp/reports
No scribe access token provided, skip sending report!
class TestImportTime:
tests: 2 failed: 0 skipped: 0 errored: 0
run_time: 1.85 seconds
avg_time: 0.93 seconds
median_time: 0.93 seconds
2 longest tests:
test_time_cuda_device_count time: 1.10 seconds
test_time_import_torch time: 0.75 seconds
Total runtime is 0:00:01
2 longest tests of entire run:
TestImportTime.test_time_cuda_device_count time: 1.10 seconds
TestImportTime.test_time_import_torch time: 0.75 seconds
```
Reviewed By: driazati
Differential Revision: D27770908
Pulled By: samestep
fbshipit-source-id: 01bbf5a339f41d3a1f493e6fa8c946ff7567daec
