Specify the subscribed topic name in topic statistics

[snehaldb90]

Enhancement in #118

Now the SubscriberTopicStatisticsNode class subscribes to multiple topic for statistics collection.
However, we cannot distinguish for which topic the statistics are collected because the topic name is not specified in the statistics.

Description

Every statistic output should specify what topic it is a measurement of.

Test Plan

• Manual testing
• Unit test
• Update e2e test

Documentation Plan

• Docstrings

Release Plan

• check in PR

Acceptance Criteria

• Code has been implemented, reviewed and merged.
• Test plan has been completed
• Release plan has been completed

Once all above items are checked, this story can be moved to done.

Resources

Class to modify: SubscriberTopicStatistics