patch 8.2.3628: looking terminal colors is a bit slow

Problem:    Looking terminal colors is a bit slow.
Solution:   Cache the terminal colors. (closes #9130, closes #9058)
diff --git a/src/option.c b/src/option.c
index 4f080a3..b807b9b 100644
--- a/src/option.c
+++ b/src/option.c
@@ -3259,6 +3259,10 @@
 	    init_highlight(TRUE, FALSE);
 	}
 # endif
+# ifdef FEAT_TERMINAL
+	term_update_colors_all();
+	term_update_wincolor_all();
+# endif
     }
 #endif