[FIX] stock: remove incorrect placeholder + default search

It's not possible to copy paste in the lot_name directly. It has been
remove since the import button.

Also add by default a search on hand in the quant view from the
stock.move.line. We don't want to show quant already send to customer
location or without quantity

Part-of: odoo/odoo#141272

addons/mrp/wizard/stock_assign_serial_numbers.xml

@@ -23,7 +23,7 @@
                     </group>
                 </group>
                 <group>
-                    <field name="serial_numbers" placeholder="copy paste a list and/or use Generate"/>
+                    <field name="serial_numbers" placeholder="e.g. SN0000001"/>
                 </group>
                 <field name="multiple_lot_components_names" invisible="1"/>
                 <group col="1">

addons/stock/static/src/fields/stock_move_line_x2_many_field.js

@@ -36,6 +36,7 @@ export class SMLX2ManyField extends X2ManyField {
             ...context,
             single_product: true,
             tree_view_ref: "stock.view_stock_quant_tree_simple",
+            search_default_on_hand: true,
         };
         const productName = this.props.record.data.product_id[1];
         const title = _t("Add line: %s", productName);

addons/stock/views/stock_move_views.xml

@@ -216,7 +216,7 @@
                             'default_product_id': parent.product_id,
                         }"/>
                     <field name="lot_name" string="Lot/Serial Number" groups="stock.group_production_lot"
-                        placeholder="Write your SN/LN one by one or copy paste a list."
+                        placeholder="e.g. SN000001"
                         column_invisible="parent.has_tracking == 'none' or not parent.show_lots_text"
                         readonly="package_level_id and parent.picking_type_entire_packs"/>
                     <field name="location_dest_id"