refactor: improve code quality and efficiency in various files (#548)

- Replace loadConfig() with _ = loadConfig()
- Update file permissions from 0660 to 0o660
- Simplify variable declarations
- Replace golang.org/x/crypto/ssh/terminal with golang.org/x/term
- Remove unused getCertPrincipals function
- Replace time.Now().Sub() with time.Since()
- Add test for ArgToIndex function

Signed-off-by: appleboy <appleboy.tw@gmail.com>

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Reviewed-on: https://gitea.com/gitea/tea/pulls/548
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Reviewed-by: techknowlogick <techknowlogick@noreply.gitea.io>
Co-authored-by: appleboy <appleboy.tw@gmail.com>
Co-committed-by: appleboy <appleboy.tw@gmail.com>

modules/print/table.go

@@ -66,7 +66,6 @@ func (t *table) sort(column uint, desc bool) {
 func (t table) Len() int      { return len(t.values) }
 func (t table) Swap(i, j int) { t.values[i], t.values[j] = t.values[j], t.values[i] }
 func (t table) Less(i, j int) bool {
-	const column = 0
 	if t.sortDesc {
 		i, j = j, i
 	}