Add aten_hardtanh_backward function

[xiaowuhu]

Depends on #1707, will add unit test after #1707 merged.

[codecov]

Codecov Report

Attention: Patch coverage is 25.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 75.20%. Comparing base (619f5ed) to head (1149291).

Files	Patch %	Lines
onnxscript/function_libs/torch_lib/ops/nn.py	25.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1715      +/-   ##
==========================================
- Coverage   75.24%   75.20%   -0.04%     
==========================================
  Files         242      242              
  Lines       25854    25857       +3     
  Branches     4658     4659       +1     
==========================================
- Hits        19453    19446       -7     
- Misses       5515     5523       +8     
- Partials      886      888       +2     

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[github-actions]

Test Results

     27 files  +     1       27 suites  +1   3h 23m 13s ⏱️ + 7m 39s
 10 515 tests ±     0    8 590 ✅  -     2    1 922 💤 ±     0  3 ❌ +2 
506 276 runs  +19 722  103 290 ✅ +4 287  402 983 💤 +15 433  3 ❌ +2 

For more details on these failures, see this check.

Results for commit 0bacde6. ± Comparison against base commit e824285.