EventsSDK: Add debug mode

[ejaffee01]

Add a debug flag to AnalyticsConfig. When set to true events will not be sent to the Events API and additional information will be logged to console. The added logs are:

• The AnalyticsConfig following the construction.
• The Payload following the call to with
• The two payloads that are passed into the merge function
• The final request body that would be sent to the Events API
  • Will specify if fetch or beacon would be used
  • Will specify request url would be used
  • Will specify if session tracking is enabled
  • Explains to disable debug flag in order to actually fire the event

J=FUS-6239
R=abenno, mtian
TEST=manual

Enabled the debug mode in the test site. See screenshots below for logging examples.

[ejaffee01]

Coverage check is failing, but I think that may be okay for this commit. The coverage is still > 80%, and there is not really unit tests to write for the additions made in this PR. We could test what is expected to will print out in the logs, but I think that may be overkill.

[ejaffee01]

Updated screenshots with logs in Chrome (fetch) with session tracking disabled and firefox (beacon) with session tracking enabled:

[mtian725]

Left some comments

[ejaffee01]

Updated screenshots

[ejaffee01]

Updated screenshot: