Add deepgrow dataset

[YuanTingHsieh]

Description

Add dataset functionalities for deepgrow application
This PR is part of the original PR (#1395) with updated tests and docstrings

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 --codeformat --coverage.
• Quick tests passed locally by running ./runtests.sh --quick.
• In-line docstrings updated.
• Documentation updated, tested make html command in the docs/ folder.

[SachidanandAlle]

LGTM, we can add the reference of original PR #1395 in the description and assign to MONAI developers for final review

[wyli]

thanks please see some comments inline

[wyli]

thanks!