Fit and Finish UX Fixes

[jowg-amazon]

Description

Addresses the fit and finish UX changes. Changes in this PR include:

• Add a delete detector bulk action button to the left of the search bar instead of under actions
  

• Change getting started to get started
  

• Move refresh and action buttons inside the table on threat detectors page
  

• Move the tabs to the top of the page for findings and alerts pages
  
  

• Add plus icon to left of create detector button
  

• Make search bar and filters compressed
  

• Change content panel title from H2 small to H3 small
  

• Fix spacing between all pages sections (16px)
  

• Remove hover state from empty message for Overview page widgets
  

• Change "total active alerts" to "total active threat alerts"
  

• Fix padding to 16px for all content panels
  

• Add period to end of correlate events description
  

• Fixes spacing from header to content when newHomePage isn't enabled

Issues Resolved

[List any issues this PR will resolve]

Check List

• Commits are signed per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[jowg-amazon]

Cypress tests passed locally

       Spec                                              Tests  Passing  Failing  Pending  Skipped  
  ┌────────────────────────────────────────────────────────────────────────────────────────────────┐
  │ ✔  1_detectors.spec.js                      02:35       14       14        -        -        - │
  ├────────────────────────────────────────────────────────────────────────────────────────────────┤
  │ ✔  2_rules.spec.js                          02:11       17       17        -        -        - │
  ├────────────────────────────────────────────────────────────────────────────────────────────────┤
  │ ✔  3_alerts.spec.js                         02:51        7        7        -        -        - │
  ├────────────────────────────────────────────────────────────────────────────────────────────────┤
  │ ✔  4_findings.spec.js                       01:43        7        6        -        1        - │
  └────────────────────────────────────────────────────────────────────────────────────────────────┘
    ✔  All specs passed!                        09:21       45       44        -        1        -  

[AWSHurneyt]

Changes LGTM.