Add blossom pre-merge pipeline (1/July)

[madil90]

Fixes #2381 .

Description

Adds the action for launching jobs when a '/build' comment is posted by an authorized user. This CI job launches pre-merge tests using NVIDIA's blossom CI system.

Status

Ready

Types of changes

• Non-breaking change (fix or new feature that would not break existing functionality).
• Breaking change (fix or new feature that would cause existing functionality to change).
• New tests added to cover the changes.
• Integration tests passed locally by running ./runtests.sh -f -u --net --coverage.
• Quick tests passed locally by running ./runtests.sh --quick --unittests.
• In-line docstrings updated.
• Documentation updated, tested make html command in the docs/ folder.

[wyli]

• we'll trigger the tests for all the PRs, so perhaps commenting /build will be noisy (repo watchers get many not that useful notifications). is it possible to trigger CI by labelling the pull request? such as https://stackoverflow.com/questions/62325286/run-github-actions-when-pull-requests-have-a-specific-label
• is this concurrency limit useful for this workflow as well?
  

  MONAI/.github/workflows/pythonapp.yml

  Lines 12 to 15 in 82fc4c1

  	concurrency:
  	# automatically cancel the previously triggered workflows when there's a newer version
  	group: build-${{ github.event.pull_request.number || github.ref }}
  	cancel-in-progress: true

• will this checkout a fork properly?
  

  MONAI/.github/workflows/blossom-ci.yml

  Lines 37 to 39 in f49712f

  	steps:
  	- name: Checkout code
  	uses: actions/checkout@v2

[madil90]

• The requirement to comment '/build' is from Blossom team. We can switch to label based system after discussing with them.
• Added the concurrency change
• Yes the checkout has been tested on a fork of MONAI and works with PRs properly.

[wyli]

Could you please sign this commit @madil90 https://github.com/Project-MONAI/MONAI/pull/2382/checks?check_run_id=2853880771

[madil90]

@wyli signed.

[wyli]

thanks!