Add tests for sync, wifi, and push

[NotWoods]

In addition to lots of tests, there has been some cleanup:

• SyncedTabsIntegration takes in syncedTabsStorage, instead of using context to get syncedTabsStorage from components.
• WifiConnectionMonitor now uses the Observable code from AC instead of re-implementing the observable pattern.
• SitePermissionsWifiIntegration has been updated to call AC observation methods

[codecov-commenter]

Codecov Report

Merging #12581 into master will increase coverage by 0.39%.
The diff coverage is 94.73%.

@@             Coverage Diff              @@
##             master   #12581      +/-   ##
============================================
+ Coverage     25.15%   25.54%   +0.39%     
- Complexity      845      866      +21     
============================================
  Files           389      389              
  Lines         15700    15687      -13     
  Branches       2022     2020       -2     
============================================
+ Hits           3949     4008      +59     
+ Misses        11444    11371      -73     
- Partials        307      308       +1     

Impacted Files	Coverage Δ	Complexity Δ
...va/org/mozilla/fenix/sync/SyncedTabsIntegration.kt	100.00% <ø> (+100.00%)	2.00 <0.00> (+2.00)
...va/org/mozilla/fenix/wifi/WifiConnectionMonitor.kt	94.44% <87.50%> (+94.44%)	5.00 <1.00> (+5.00)
...in/java/org/mozilla/fenix/components/Components.kt	30.00% <100.00%> (ø)	1.00 <0.00> (ø)
...ava/org/mozilla/fenix/sync/SyncedTabsViewHolder.kt	100.00% <100.00%> (+100.00%)	1.00 <0.00> (+1.00)
...zilla/fenix/wifi/SitePermissionsWifiIntegration.kt	100.00% <100.00%> (+100.00%)	10.00 <5.00> (+10.00)
...n/java/org/mozilla/fenix/sync/SyncedTabsAdapter.kt	10.00% <0.00%> (+10.00%)	0.00% <0.00%> (ø%)
... and 1 more

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[jonalmeida]

Please don't land this without testing the feature carefully. If I recall correctly, this causes a cyclic dependency, which is why we accessed the storage via the context instead of passing it in through he constructor.