Fix virial

[HuangJiameng]

https://github.com/deepmodeling/dpdata/discussions/319
now user can extract the virial data using "cp2k/aimd_output"

[codecov-commenter]

Codecov Report

Merging #324 (43f5a05) into devel (7029230) will increase coverage by 0.54%.
The diff coverage is 82.20%.

@@            Coverage Diff             @@
##            devel     #324      +/-   ##
==========================================
+ Coverage   81.48%   82.03%   +0.54%     
==========================================
  Files          61       65       +4     
  Lines        5143     5660     +517     
==========================================
+ Hits         4191     4643     +452     
- Misses        952     1017      +65     

Impacted Files	Coverage Δ
dpdata/cli.py	0.00% <0.00%> (ø)
dpdata/unit.py	88.15% <ø> (ø)
dpdata/plugins/amber.py	64.40% <33.33%> (-21.31%)	⬇️
dpdata/plugins/deepmd.py	62.50% <45.83%> (-31.38%)	⬇️
dpdata/plugins/gaussian.py	62.22% <46.87%> (-37.78%)	⬇️
dpdata/gaussian/gjf.py	74.75% <74.75%> (ø)
dpdata/driver.py	86.36% <86.36%> (ø)
dpdata/system.py	84.70% <87.80%> (+4.61%)	⬆️
dpdata/plugins/ase.py	74.32% <90.24%> (+8.86%)	⬆️
dpdata/ase_calculator.py	92.59% <92.59%> (ø)
... and 21 more

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[robinzyb]

please add unittest for stress parser.

[HuangJiameng]

please add unittest for stress parser.

OK