Add sidestream to BQ update-schema

[stephen-soltesz]

This change adds support for updating the sidestream BQ tables using update-schema.

This change is in service of automatically expanding the legacy tables to support the new annotation-service fields.

This change also fixes a bug in the etl/schema unit tests by adding the m.Run() which was previously missing.

Testing: verified to WAI on mlab-sandbox.batch.sidestream and mlab-sandbox.base_tables.sidestream tables. This change removes "Description" fields (though they are currently very sparse; more thorough descriptions should be added during standard column migration).

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This change is 

[coveralls]

Pull Request Test Coverage Report for Build 6410

• 8 of 36 (22.22%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-4.03%) to 62.529%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
schema/sidestream_schema.go	8	36	22.22%
<!--	Total:	8	36	22.22%	-->

Totals
Change from base Build 6404:	-4.03%
Covered Lines:	3471
Relevant Lines:	5551

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💛 - Coveralls