Protect: Cache empty results for a shorter period of time

[leogermani]

Changes proposed in this Pull Request:

• Cache empty results for a shorter period of time
• Add tests :)
• Fix a small bug in get_all_vulnerabitlities()

Jetpack product discussion

1202064326332560-as-1202246145491819

Does this pull request change what data or activity we track or use?

Testing instructions:

• Set your response type as empty
• Connect Protect and load the page
• Check your jetpack_protect_status_time option and verify it is a timestamp for only 5 minutes in the future

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  • https://app.asana.com/0/0/1202246145491819

[github-actions]

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Protect plugin:

• Next scheduled release: June 7, 2022.
• Scheduled code freeze: May 30, 2022.

[retrofox]

LGTM.

Confirmed the timestamp is five minutes when empty state:

> jetpack docker wp option get jetpack_protect_status_time
1652439562

complete status

And it's twelve hours when complete:

jetpack docker wp option get jetpack_protect_status_time
1652482357

[leogermani]

I love the illustrated testing report! Thanks.

There are some failing tests in some PHP versions I'll have to fix