[0.9.x] Add int8 command

[xinyu-intel]

Description

(Brief description on what this PR is about)

Checklist

Essentials

• PR's title starts with a category (e.g. [BUGFIX], [MODEL], [TUTORIAL], [FEATURE], [DOC], etc)
• Changes are complete (i.e. I finished coding on this PR)
• All changes have test coverage
• Code is well-documented

Changes

• Feature1, tests, (and when applicable, API doc)
• Feature2, tests, (and when applicable, API doc)

Comments

• If this change is a backward incompatible change, why must this change be made.
• Interesting edge cases to note here

cc @dmlc/gluon-nlp-team

[codecov]

Codecov Report

Merging #1174 into v0.9.x will increase coverage by 19.62%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           v0.9.x   #1174       +/-   ##
==========================================
+ Coverage   68.88%   88.5%   +19.62%     
==========================================
  Files          72      72               
  Lines        6970    6970               
==========================================
+ Hits         4801    6169     +1368     
+ Misses       2169     801     -1368

Impacted Files	Coverage Δ
src/gluonnlp/data/word_embedding_evaluation.py	89.31% <0%> (-6.88%)	⬇️
src/gluonnlp/data/glue.py	96.81% <0%> (-1.82%)	⬇️
src/gluonnlp/model/sequence_sampler.py	36.33% <0%> (+3.11%)	⬆️
src/gluonnlp/model/bert.py	94.62% <0%> (+3.28%)	⬆️
src/gluonnlp/embedding/evaluation.py	95.79% <0%> (+4.2%)	⬆️
src/gluonnlp/utils/files.py	42.62% <0%> (+4.91%)	⬆️
src/gluonnlp/model/train/language_model.py	90.32% <0%> (+5.06%)	⬆️
src/gluonnlp/model/bilm_encoder.py	100% <0%> (+5.08%)	⬆️
src/gluonnlp/model/convolutional_encoder.py	97.67% <0%> (+6.97%)	⬆️
src/gluonnlp/model/parameter.py	100% <0%> (+8%)	⬆️
... and 35 more

[mli]

Job PR-1174/2 is complete.
Docs are uploaded to http://gluon-nlp-staging.s3-accelerate.dualstack.amazonaws.com/PR-1174/2/index.html