Adding support for content type to GCS output

[P1llus]

Content type headers are not set for objects automatically when running against local system tests (like emulators), needs a way to set it correctly.

Added it as a configurable option so we can test multiple content types.

[elasticmachine]

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• Start Time: 2023-01-30T10:17:20.625+0000

• Duration: 5 min 25 sec

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Test	Results
Failed	0
Passed	21
Skipped	0
Total	21

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