Add ArchiveSize and FileSize to parser records

[stephen-soltesz]

This change adds two new fields to the ParseInfo record for all datatypes:

• ArchiveSize - The original archive size as found in GCS.
• FileSize - The size of the file data provided to the parser.

To populate the ArchiveSize field, this change adds GetSize() to the TestSource interface and GCSSource implementation.

Part of:

• Add ArchiveSize and FileSize attribute to the ParseInfo structure #1116

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This change is 

[cristinaleonr]

Reviewable status: complete! 1 of 1 approvals obtained

[stephen-soltesz]

Uh oh -- we're doin' it!

Thank you!