Adding grey backgrounds, white boxes and aligning items

[damianpm]

What this PR does / why we need it:

It continues with the implementation of visual context for PF4 cards, tables and lists initiated in #1182

Which issue(s) this PR fixes

https://issues.jboss.org/browse/THREESCALE-3448

Please browse in all pages you can

[codecov]

Codecov Report

Merging #1237 into content-bg-and-cards-proof-of-concept will decrease coverage by 0.89%.
The diff coverage is n/a.

@@                           Coverage Diff                            @@
##           content-bg-and-cards-proof-of-concept    #1237     +/-   ##
========================================================================
- Coverage                                  92.55%   91.66%   -0.9%     
========================================================================
  Files                                       2457     2325    -132     
  Lines                                      80171    74674   -5497     
========================================================================
- Hits                                       74205    68448   -5757     
- Misses                                      5966     6226    +260

Impacted Files	Coverage Δ
app/lib/logic/nginx_proxy.rb	27.27% <0%> (-72.73%)	⬇️
app/helpers/support_entitlements_helper.rb	33.33% <0%> (-66.67%)	⬇️
app/lib/three_scale/email_sanitizer.rb	25% <0%> (-66.67%)	⬇️
lib/range_hacks.rb	37.5% <0%> (-62.5%)	⬇️
app/lib/events/importers/first_traffic_importer.rb	40% <0%> (-60%)	⬇️
app/queries/auto_account_deletion_queries.rb	40% <0%> (-60%)	⬇️
app/workers/purge_old_user_sessions_worker.rb	40% <0%> (-60%)	⬇️
app/models/numeric_hash.rb	41.17% <0%> (-58.83%)	⬇️
app/helpers/google_experiments_helper.rb	28.57% <0%> (-57.15%)	⬇️
...orkers/service_discovery/refresh_service_worker.rb	44.44% <0%> (-55.56%)	⬇️
... and 326 more

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