Sync stats expansion & refactor

[beidouz]

Notice

It is not allowed to submit your PR to the master branch directly, please submit your PR to the master-pre-merge branch.

Description

Please include a brief summary of the change that this pull request proposes. Include any relevant motivation and context. List any dependencies required for this change.

• Created statsTrackers to store different types of sync stats functionalities
• Added BLOCKS, RECEIPTS and TRIE_DATA to the enum RequestType
• Refactored ResponseStatsTracker to avoid code repetition
• Expanded Request & Response tracking to include the new request types.
• Removed use of StandaloneBlockchain from SyncStatsTest

Todo: Log statistics regarding the new types of messages from the corresponding handlers/tasks (After fast sync is merged)

Fixes Issue #837

Type of change

Insert x into the following checkboxes to confirm (eg. [x]):

• Bug fix.
• New feature.
• Enhancement.
• Unit test.
• Breaking change (a fix or feature that causes existing functionality to not work as expected).
• Requires documentation update.

Testing

Please describe the tests you used to validate this pull request. Provide any relevant details for test configurations as well as any instructions to reproduce these results.

• Fixed and added tests in SyncStatsTest

Verification

Insert x into the following checkboxes to confirm (eg. [x]):

• I have self-reviewed my own code and conformed to the style guidelines of this project.
• New and existing tests pass locally with my changes.
• I have added tests for my fix or feature.
• I have made appropriate changes to the corresponding documentation.
• My code generates no new warnings.
• Any dependent changes have been made.

[AlexandraRoatis]

The functionality looks good, but I'd like some more code cleanup before we merge this (as described in the comments). Also, please ensure full test coverage of the tracker classes.

[AionJayT]

LGTM