download cosign releases from GitHub rather than GCS (#126) #292

Job	Run time
Install Cosign v0.6.0 and test presence in path with pre installed libpcsclite1 package (ubuntu-l...	21s
Install Cosign and test presence in path (macos-latest)	11s
Install Cosign and test presence in path (ubuntu-latest)	8s
Install Cosign and test presence in path (windows-latest)	18s
Install Custom Cosign and test presence in path (macos-latest)	16s
Install Custom Cosign and test presence in path (ubuntu-latest)	10s
Install Custom Cosign and test presence in path (windows-latest)	19s
Install Cosign v0.6.0 and test presence in path (macos-latest)	16s
Install Cosign v0.6.0 and test presence in path (ubuntu-latest)	24s
Install Cosign v0.6.0 and test presence in path (windows-latest)	21s
Install Custom Cosign and test presence in path (macos-latest)	1m 3s
Install Custom Cosign and test presence in path (ubuntu-latest)	7s
Install Custom Cosign and test presence in path (windows-latest)	17s
Install Custom Cosign and test presence in path with custom root dir (ubuntu-latest)	5s
Try to install a wrong Cosign (macos-latest)	27s
Try to install a wrong Cosign (ubuntu-latest)	6s
Try to install a wrong Cosign (windows-latest)	12s
Try to install cosign with go 1.19	4m 9s
Try to install cosign with go 1.20	3m 50s
Try to install cosign with go 1.19	2m 54s
Try to install cosign with go 1.20	2m 31s
Try to install cosign with go 1.19	8m 19s
Try to install cosign with go 1.20	9m 24s
Install existing release of Cosign and test presence in path (ubuntu-latest)	6s
	36m 14s

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