Add bigquery tags to struct fields and create an internal directory

[SaiedKazemi]

This commit adds the missing bigquery tags to all struct fields of datatypes that are stored in BigQuery. In the legacy pipeline, we used streaming inserts, and BigQuery respected the bigquery tags. In Gardener 2.0, the rows are written to json files, and the json tags are used. Gardener then triggers the loading into BigQuery from the json files.

This commit also moves ipcache and triggertrace packages to the internal directory because these are not used externally.

Changes were tested locally with "go test -race" and "docker-compose".

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This change is 

[coveralls]

Pull Request Test Coverage Report for Build 437

• 4 of 4 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.01%) to 96.85%

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Totals
Change from base Build 434:	-0.01%
Covered Lines:	615
Relevant Lines:	635

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💛 - Coveralls

[SaiedKazemi]

Thank you @cristinaleonr .