Fix part of #1433: Introduce the Oppia Logger and move analytics logging to it

[vinitamurthi]

Explanation

This PR adds the Oppia Logger. It moves the calls of the analytics controller methods to the oppia logger and adds tests
Fixes part of #1433

Checklist

• The PR title starts with "Fix #bugnum: ", followed by a short, clear summary of the changes. (If this PR fixes part of an issue, prefix the title with "Fix part of #bugnum: ...".)
• The PR explanation includes the words "Fixes #bugnum: ..." (or "Fixes part of #bugnum" if the PR only partially fixes an issue).
• The PR follows the style guide.
• The PR does not contain any unnecessary auto-generated code from Android Studio.
• The PR is made from a branch that's not called "develop".
• The PR is made from a branch that is up-to-date with "develop".
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[Sarthak2601]

Nicely done! Just had one suggestion regarding the logging of events in AnalyticsControllerTest.kt

[Sarthak2601]

LGTM.

[BenHenning]

Thanks @vinitamurthi--left a few comments, but overall the PR LGTM.

[BenHenning]

@Sarthak2601 are you planning to provide additional feedback? Otherwise, you should de-assign yourself if you've finished reviewing the PR.

[vinitamurthi]

PTAL @BenHenning and if the changes look okay can you resolve the comments?

[BenHenning]

Thanks @vinitamurthi. The PR LGTM--feel free to resolve my comment directly once it's addressed or reassign this PR to me if you have follow-up questions.