feat: InspectableWebview preference

[breautek]

Platforms affected

Motivation and Context

Sister PR of apache/cordova-ios#1300
Makes cordova-android honour the InspectableWebview preference in a similar fashion the iOS platform.

Description

Like iOS, android will default to the original method of choosing if the inspecter should be enabled based on the module's debuggable flag. So if the preference is unset, the inspecter will be enabled on debug builds, and disabled on release builds.

If the preference is set and if, and only if the value is "true", the webview inspecter will be forcefully enabled.
If the preference is set but is not "true" (including any invalid value), the webview inspector will be forcefully disabled.

Unlike iOS, Android has had the ability to independently control the inspecter programmatically for some time, so there is no Android OS limitation.

Testing

Ran npm test
Manual obesrvations in HelloWorld test app.

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 #1589 (489ac98) into master (d4bfd50) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1589   +/-   ##
=======================================
  Coverage   72.13%   72.13%           
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  Files          21       21           
  Lines        1751     1751           
=======================================
  Hits         1263     1263           
  Misses        488      488           

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