[CI] Update unittests-gpu (#1313)

[barry-jin]

• [CI] Add GPU pytest + Submit jobs to AWS Batch through GitHub Actions

• [CI] Update GPU tests and parameters use

• [CI] Update CI pipeline

• [CI] Add new line

• [CI] Update pytest command for cpu test

• [CI] Update use_gpu to ctx + add permissions to test.sh

• [CI] Update submitted command

• [CI] De-stringify input to mxnet attribute

• [CI] Change pull_request event to pull_request_target event

• [CI] Add new workflow for GPU unit tests

• [CI] Update unittests-gpu.yml

• [CI] Update unittests-gpu.yml

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