[CHORE] Use github.com/ProtonMail/go-crypto

- We were previously using `github.com/keybase/go-crypto`, because the
package for openpgp by Go itself is deprecated and no longer
maintained. This library provided a maintained version of the openpgp
package. However, it hasn't seen any activity for the last five years,
 and I would therefore consider this also unmaintained.
- This patch switches the package to `github.com/ProtonMail/go-crypto`
which provides a maintained version of the openpgp package and was
already being used in the tests.
- Adds unit tests, I've carefully checked the callstacks to ensure the
OpenPGP-related code was covered under either a unit test or integration
tests to avoid regression, as this can easily turn into security
vulnerabilities if a regression happens here.
- Small behavior update, revocations are now checked correctly instead
of checking if they merely exist and the expiry time of a subkey is used
if one is provided (this is just cosmetic and doesn't impact security).
- One more dependency eliminated :D

models/asymkey/gpg_key_test.go

@@ -13,7 +13,7 @@ import (
 	"code.gitea.io/gitea/modules/timeutil"
 	"code.gitea.io/gitea/modules/util"
 
-	"github.com/keybase/go-crypto/openpgp/packet"
+	"github.com/ProtonMail/go-crypto/openpgp/packet"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -241,6 +241,66 @@ Q0KHb+QcycSgbDx0ZAvdIacuKvBBcbxrsmFUI4LR+oIup0G9gUc0roPvr014jYQL
 	}
 }
 
+func TestCheckGPGRevokedIdentity(t *testing.T) {
+	assert.NoError(t, unittest.PrepareTestDatabase())
+
+	assert.NoError(t, db.Insert(db.DefaultContext, &user_model.EmailAddress{UID: 1, Email: "no-reply@golang.com", IsActivated: true}))
+	assert.NoError(t, db.Insert(db.DefaultContext, &user_model.EmailAddress{UID: 1, Email: "revoked@golang.com", IsActivated: true}))
+	_ = unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 1})
+
+	revokedUserKey := `-----BEGIN PGP PUBLIC KEY BLOCK-----
+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+DXzSiOU/SUA42mmG+5kjF8Aabq9wPwT9wjraHShEweNerNMmOqJExBOy3yFeyDpa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+=IKnw
+-----END PGP PUBLIC KEY BLOCK-----
+`
+
+	keys, err := AddGPGKey(db.DefaultContext, 1, revokedUserKey, "", "")
+	assert.NoError(t, err)
+	assert.Len(t, keys, 1)
+	assert.Len(t, keys[0].Emails, 1)
+	assert.EqualValues(t, "no-reply@golang.com", keys[0].Emails[0].Email)
+
+	primaryKeyID := "D68172F48E9C5283"
+	// Assert primary key
+	unittest.AssertExistsAndLoadBean(t, &GPGKey{OwnerID: 1, KeyID: primaryKeyID, Content: "xsBNBFsgO5EBCADhREPmcjsPkXe1z7ctvyWL0S7oa9JaoGZ9oPDHFDlQxd0qlX2eDZJZDg0qYvVixmaULIulApq1puEsaJCn3lHUbHlb4PYKwLEywYXM28JN91KtLsz/uaEX2KC5WqeP40utmzkNLq+oRX/xnRMgwbO7yUNVG2UlEa6eI+xOXO3YtLdmJMBWClQ066ZnOIzEo1JxnIwha1CDBMWLLfOLrg6l8InUqaXbtEBbnaIYO6fXVXELUjkxnmk7t/QOk0tXCy8muH9UDqJkwDUESY2l79XwBAcx9riX8vY7vwC34pm22fAUVLCJx1SJx0J8bkeNp38jKM2Zd9SUQqSbfBopQ4pPABEBAAE="})
+	// Assert subkey
+	unittest.AssertExistsAndLoadBean(t, &GPGKey{OwnerID: 1, KeyID: "2C56900BE5486AF8", PrimaryKeyID: primaryKeyID, Content: "zsBNBFsgO5EBCAC5INOERA2aNSYHWFeMfByShUuMQGFmyL2tWT6rwzZmUVG0GUdvoKSRhMJ+81aHxr5zmIhluegEuY99UhX+ZK6NftW2UOYjjjQZ4NPDjqOfP5dYUbHiCFRgeUxkmjwnQoSih63iSOoUt5kocR+oXXxbYmbgeOa8KGgKzDLGHI2nsy8Cni3N/enKVMMHGbJy1DXdV7uRFhBdjnRZGdmtamHcQbwGHUH+PtTa/jUSMdbtTUvXPI6dz7jDpK0BImzbXNb+r9CcudpiixuMu5gv3qyJL5EAWCXcT2j+y2VWj2HN/8bJHMoo6yf+bn6A/Cu9f0obbGVF0kJ/Y5UWmEdBG6IzABEBAAE="})
+}
+
 func TestCheckGParseGPGExpire(t *testing.T) {
 	testIssue6599 := `-----BEGIN PGP PUBLIC KEY BLOCK-----