Consistent usage of ContainerAware

[mikkamp]

Changes proposed in this Pull Request:

This PR standardizes the usage of ContainerAware across various classes. This makes it more consistent with what was decided in issue #563

I've also fixed some of the AdminConditional loading to ensure that some of the classes are not loaded on the frontend.
I was considering adding is_admin() && ! wp_doing_ajax() to the AdminConditional. But for now I left it since there could be a possibility that coupon bulk editing or activating plugin is done through an ajax request, which might silently break some of the actions. So for now I've left it as we'd need to do some extensive testing to make sure we aren't missing any ajax requests.

When looking at a front end request we can thus see a small decrease in the time spent resolving classes.

Before:

After:

PR #2758 takes that a step further. We can still decrease it even more, but considering that it needs specific testing for each change, I think it's better to improve that through multiple separate PR's.

Closes #563

Detailed test instructions:

1. Test some basic REST API requests while going through onboarding
2. As well as going through some of the extension pages
3. Confirm that none of the requests fail

Changelog entry

• Tweak - Consistent usage of ContainerAware.

[codecov]

Codecov Report

Attention: Patch coverage is 58.82353% with 7 lines in your changes missing coverage. Please review.

Project coverage is 67.0%. Comparing base (c8c1efa) to head (763cde0).
Report is 25 commits behind head on develop.

Files with missing lines	Patch %	Lines
...ernal/DependencyManagement/CoreServiceProvider.php	0.0%	7 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             develop   #2761     +/-   ##
===========================================
- Coverage       67.0%   67.0%   -0.1%     
+ Complexity      4692    4684      -8     
===========================================
  Files            480     480             
  Lines          19601   19581     -20     
===========================================
- Hits           13141   13116     -25     
- Misses          6460    6465      +5     

Flag	Coverage Δ
php-unit-tests	67.0% <58.8%> (-0.1%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/API/Google/Middleware.php	95.7% <ø> (-<0.1%)	⬇️
src/API/Google/Settings.php	6.3% <ø> (-1.2%)	⬇️
src/API/Site/Controllers/Ads/ReportsController.php	93.8% <ø> (ø)
src/API/Site/Controllers/BaseReportsController.php	75.9% <ø> (-0.8%)	⬇️
...e/Controllers/MerchantCenter/ReportsController.php	91.8% <ø> (ø)
...trollers/MerchantCenter/ShippingTimeController.php	92.9% <ø> (-0.1%)	⬇️
src/API/Site/RESTControllers.php	100.0% <ø> (+14.3%)	⬆️
src/Admin/BulkEdit/BulkEditInitializer.php	66.7% <ø> (ø)
src/Ads/AccountService.php	98.7% <100.0%> (-<0.1%)	⬇️
src/ConnectionTest.php	0.0% <ø> (ø)
... and 5 more

... and 1 file with indirect coverage changes

[ianlin]

Thanks for refactoring to use ContainerAware consistently and also add / fix the conditional loading for some classes . I have gone through the onboarding and tested all the pages within the extension, the requests were successful as normal.