feat(ssh): auto generate additional ssh keys (#33974)

adds capabilities for gitea to generate ecdsa and ed25519 keys by
default
adds cli for built-in ssh key generation helpers


closes: https://github.com/go-gitea/gitea/issues/33783

---------

Co-authored-by: Nicolas <bircni@icloud.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: Giteabot <teabot@gitea.io>

tests/integration/git_helper_for_declarative_test.go

@@ -15,6 +15,7 @@ import (
 	"testing"
 	"time"
 
+	"gitea.dev/modules/generate"
 	"gitea.dev/modules/git"
 	"gitea.dev/modules/git/gitcmd"
 	"gitea.dev/modules/setting"
@@ -33,7 +34,7 @@ func withKeyFile(t *testing.T, keyname string, callback func(string)) {
 	assert.NoError(t, err)
 
 	keyFile := filepath.Join(tmpDir, keyname)
-	err = ssh.GenKeyPair(keyFile)
+	err = ssh.GenKeyPair(keyFile, generate.SSHKeyECDSA, 0)
 	assert.NoError(t, err)
 
 	err = os.WriteFile(filepath.Join(tmpDir, "ssh"), []byte("#!/bin/bash\n"+