adding some new tests for endpoints

[TimothyMothra]

Fix Issue #1648
Originally reported #1637

Changes

• Fix for ServerTelemetryChannel to not overwrite endpoint coming from config in Initialize method.
• Fix for QuickPulseTelemetryModule to set endpoint on QuickPulseTelemetryProcessor during RegisterTelemetryProcessor method.
• Add new tests for the above scenarios.

Checklist

• I ran Unit Tests locally.
• CHANGELOG.md updated with one line description of the fix, and a link to the original issue if available.

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• Design discussion issue #
• Changes in public surface reviewed

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[TimothyMothra]

Note to self: removing the line in Initialize causes all of the "VerifyEndpointConnectionString_SetFromInitialize" tests to fail.

[TimothyMothra]

Note to self: investigate setting endpoints on TelemetryModules.

TODO Confirm:

• manual set, before Factory
• manual set, after Factory