feat issue 1027: Add data set and member listing via FTP

[lauren-li]

Proposed changes

Note: The contents of branch v1.11.x should be merged into master before this PR. (It will also be easier to review once v1.11.x is merged in.)

This PR is initial work to address issue #1027 (MVS for FTP package).

In Zowe Explorer, testers should now be able to:

• Add zftp profiles to the Data Sets view
• Use a zftp profile to list data sets
• Use a zftp profile to list all members of a PDS

Additionally, some refactoring was done to reuse common code between the FTP USS and MVS API classes.

Gif:

Release Notes

Milestone: 1.2.0

Changelog: Add ability to list data sets and data set members using FTP.

Types of changes

What types of changes does your code introduce to Zowe Explorer?
Put an x in the boxes that apply

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Updates to Documentation or Tests (if none of the other choices apply)

Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This checklist will be used as reference for both the contributor and the reviewer

• I have read the CONTRIBUTOR GUIDANCE wiki
• PR title follows Conventional Commits Guidelines
• PR Description is included
• gif or screenshot is included if visual changes are made
• yarn workspace vscode-extension-for-zowe vscode:prepublish has been executed
• All checks have passed (DCO, Jenkins and Code Coverage)
• I have added unit test and it is passing
• I have added integration test and it is passing
• There is coverage for the code that I have added
• I have tested it manually and there are no regressions found
• I have added necessary documentation (if appropriate)
• Any PR dependencies have been merged and published (if appropriate)

[lauren-li]

Closing in favor of PR #1219.