[FIX] base_import_map: prevent duplicate map settings controls

Because in the custom init function the original (prototype) 'opts' array
was mutated, every time the function was called (which happens everytime one
opens the import wizard) 3 opts were added, resulting in duplicate map
controls.
Solve the bug by using concat + reassignment instead of mutation.

base_import_map/static/src/js/base_import_map.js

@@ -11,9 +11,15 @@ odoo.define('base_import_map.map', function (require) {
 
     BaseImport.DataImport.include({
         init: function() {
-            this.opts.push({name: 'settings', label: _lt("Settings:"), value: ''});
-            this.opts.push({name: 'save_settings', label: _lt("Save settings:"), value: ''});
-            this.opts.push({name: 'file_read_hook', label: _lt("File read hook:"), value: ''});
+            // Assign a new array instead of pushing values to the
+            // original one, because otherwise we would change the
+            // prototype array, meaning that each time 'init' is called
+            // the values are pushed again, resulting in duplicate entries
+            this.opts = this.opts.concat([
+                {name: 'settings', label: _lt("Settings:"), value: ''},
+                {name: 'save_settings', label: _lt("Save settings:"), value: ''},
+                {name: 'file_read_hook', label: _lt("File read hook:"), value: ''}
+            ])
             this._super.apply(this, arguments);
         },
         start: function() {