fix!: Make CoreAndroid plugin instantiate on load

[breautek]

I don't anticipate breaking changes from this change, however it is a difference in behaviour since CoreAndroid won't be lazily loaded, therefore I've marked this commit has a breaking change.

Platforms affected

Android / CoreAndroid plugin

Motivation and Context

CoreAndroid was lazily loaded via getPlugin call. This can create a race condition in some situations, particularly
with a new feature in the works: #1574 where onRenderProcessGone may be invoked before anything gets a chance to call getPlugin for CoreAndroid.

In general, because this is Core plugin, I feel like it should always be loaded in, not lazily loaded in.

Description

Inside PluginManager, I added a new public API: addService(String serviceName, String className, bool onload).
The addService(String serviceName, String className) implementation has been moved to the new public API.

CordovaWebviewImpl will now add the CoreAndroid service with onload set to true.

Testing

Ran npm test on linux.
Also manual test while testing the onRenderProcessGone PR.

Checklist

• I've run the tests to see all new and existing tests pass
• I added automated test coverage as appropriate for this change
• Commit is prefixed with (platform) if this change only applies to one platform (e.g. (android))
• If this Pull Request resolves an issue, I linked to the issue in the text above (and used the correct keyword to close issues using keywords)
• I've updated the documentation if necessary

[codecov-commenter]

Codecov Report

Merging #1605 (57369f3) into master (2252c09) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1605   +/-   ##
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  Coverage   71.82%   71.82%           
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  Files          23       23           
  Lines        1796     1796           
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  Hits         1290     1290           
  Misses        506      506           

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[dpogue]

LGTM