Add hide & show alert status actions

[moolitayer]

This should provide all the backend support needed to support hiding alert statuses for the alert screen.
Implemented using a new hide action_type

The api can be used to filter based on visibility:

localhost:3000/api/alerts?filter[]=hidden?=true&expand=resources

We also support making them visible again with a show action_type.

[moolitayer]

@simon3z this will provide the feature we discussed. hidden != resolved

fyi @jeff-phillips-18 @serenamarie125 If we will choose to include this in the future,
it would require ability for new actions: hide & show as well ability to show/hide 'hidden' alerts.

[miq-bot]

Checked commit moolitayer@47f08d5 with ruby 2.2.6, rubocop 0.47.1, and haml-lint 0.20.0
3 files checked, 2 offenses detected

app/models/miq_alert_status_action.rb

• ❗ - Line 18, Col 8 - Style/WordArray - Use %w or %W for an array of words.
• ❗ - Line 19, Col 9 - Style/MultilineOperationIndentation - Align the operands of a condition in an if statement spanning multiple lines.

[moolitayer]

@gtanzillo can you please review this PR or assign someone to review it

[gtanzillo]

👍 LGTM

[moolitayer]

Thanks for you time @gtanzillo 🍺

[gtanzillo]

No problem @moolitayer 🍻