chore(sec): unify usage of crypto/rand.Read (#7453)

- Unify the usage of [`crypto/rand.Read`](https://pkg.go.dev/crypto/rand#Read) to `util.CryptoRandomBytes`.
- Refactor `util.CryptoRandomBytes` to never return an error. It is documented by Go, https://go.dev/issue/66821, to always succeed. So if we still receive a error or if the returned bytes read is not equal to the expected bytes to be read we panic (just to be on the safe side).
- This simplifies a lot of code to no longer care about error handling.

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/7453
Reviewed-by: Earl Warren <earl-warren@noreply.codeberg.org>
Co-authored-by: Gusted <postmaster@gusted.xyz>
Co-committed-by: Gusted <postmaster@gusted.xyz>

cmd/generate.go

@@ -70,10 +70,7 @@ func runGenerateInternalToken(c *cli.Context) error {
 }
 
 func runGenerateLfsJwtSecret(c *cli.Context) error {
-	_, jwtSecretBase64, err := generate.NewJwtSecret()
-	if err != nil {
-		return err
-	}
+	_, jwtSecretBase64 := generate.NewJwtSecret()
 
 	fmt.Printf("%s", jwtSecretBase64)