test: Add tests for the tar writer #141

Job	Run time
Integration tests	46s
End to end tests / End to end tests (Examples/HelloWorldVapor)	1m 41s
Unit tests / Construct unit test matrix	2s
End to end tests / End to end tests (Examples/HelloWorldHummingbird)	1m 58s
Soundness / API breakage check	45s
Soundness / Broken symlinks check	2s
Soundness / Documentation check	1m 11s
Soundness / License headers check	8s
Soundness / Unacceptable language check	3s
Soundness / Format check	34s
Soundness / Python lint check	6s
Soundness / Shell check	33s
Soundness / YAML lint check	3s
Swift 6 Language Mode / Swift 6 language mode	49s
Unit tests / Unit tests / Linux (6.0)	45s
Unit tests / Unit tests / Linux (nightly-6.0)	52s
Unit tests / Unit tests / Linux (nightly-main)	52s
	11m 10s

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