Add support for the crypto refresh in v2 (#265)

This commit adds support for the OpenPGP crypto-refresh.
- Updates go-crypto dependency to v1.1.0-alpha.1
- Adapts the session key logic to handle PKESK/SKESK v6 packets without an algorithm attached
- Updates the min go version to 1.17 as requires by  go-crypto v1.1.0-alpha.1
- Update the cricl dependency to 1.3.7 matching go-crypto
Not supported:
- crypto-refresh intended recipients
- v6 key generation

go.mod

@@ -1,12 +1,20 @@
 module github.com/ProtonMail/gopenpgp/v2
 
-go 1.15
+go 1.17
 
 require (
-	github.com/ProtonMail/go-crypto v0.0.0-20230717121422-5aa5874ade95
+	github.com/ProtonMail/go-crypto v1.1.0-alpha.1
 	github.com/ProtonMail/go-mime v0.0.0-20230322103455-7d82a3887f2f
-	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/pkg/errors v0.9.1
 	github.com/stretchr/testify v1.7.0
-	golang.org/x/crypto v0.7.0
+	golang.org/x/crypto v0.17.0
+)
+
+require (
+	github.com/cloudflare/circl v1.3.7 // indirect
+	github.com/davecgh/go-spew v1.1.0 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	golang.org/x/sys v0.16.0 // indirect
+	golang.org/x/text v0.14.0 // indirect
+	gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c // indirect
 )