Adjust structure of e2e test codes

[qiuming-best]

Put every test moduels into seperate packages and all velero install parameters integrated into one struct
Signed-off-by: Ming mqiu@vmware.com

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Please add a summary of your change

It's reference to #4349, but it's just optimize the e2e codes structure, the new test cases codes will be submitted in another pr.

• Putting different test modules into separate packages, so categorize test cases may make our test codes structure more clear.(which reference to the kubernates e2e code structure)
• Integrating all velero install options parameters into one struct.

Does your change fix a particular issue?

Fixes #(issue)

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• Accepted the DCO. Commits without the DCO will delay acceptance.
• Created a changelog file or added /kind changelog-not-required.
• Updated the corresponding documentation in site/content/docs/main.

[danfengliu]

LGTM