patch 8.2.1845: Vim9: function defined in a block can't use block variables

Problem:    Vim9: function defined in a block can't use variables defined in
            that block.
Solution:   First step: Make a second hashtab that holds all script variables,
            also block-local ones, with more information.
diff --git a/src/scriptfile.c b/src/scriptfile.c
index a8e67b9..4f3e94e 100644
--- a/src/scriptfile.c
+++ b/src/scriptfile.c
@@ -1348,8 +1348,8 @@
 		}
 	}
 
-	// old imports are no longer valid
-	free_imports(sid);
+	// old imports and script variables are no longer valid
+	free_imports_and_script_vars(sid);
 
 	// in Vim9 script functions are marked deleted
 	if (is_vim9)
@@ -1375,6 +1375,7 @@
 	    // Allocate the local script variables to use for this script.
 	    new_script_vars(script_items.ga_len);
 	    ga_init2(&si->sn_var_vals, sizeof(svar_T), 10);
+	    hash_init(&si->sn_all_vars.dv_hashtab);
 	    ga_init2(&si->sn_imports, sizeof(imported_T), 10);
 	    ga_init2(&si->sn_type_list, sizeof(type_T), 10);
 # ifdef FEAT_PROFILE
@@ -1592,7 +1593,7 @@
 	vim_free(si->sn_vars);
 
 	vim_free(si->sn_name);
-	free_imports(i);
+	free_imports_and_script_vars(i);
 	free_string_option(si->sn_save_cpo);
 #  ifdef FEAT_PROFILE
 	ga_clear(&si->sn_prl_ga);