I added this
class SupplierInherit(models.Model):
_inherit = 'product.supplierinfo'
vendor_stockinfo = fields.Integer(string="Vendor Stock")<record id="inherit_supplierinfo_tree_view_vendor_stockinfo" model="ir.ui.view"><record id="product_template_form_view_inherit_override_seller_ids" model="ir.ui.view">
<field name="name">Add vendor_stockinfo to product.product_supplierinfo_tree_view</field>
<field name="model">product.supplierinfo</field>
<field name="inherit_id" ref="product.product_supplierinfo_tree_view"/>
<field name="arch" type="xml">
<xpath expr="//field[@name='product_code']" position="after">
<field name="vendor_stockinfo"/>
</xpath>
</field>
</record>
<field name="name">Override seller_ids with custom tree</field>
<field name="model">product.template</field>
<field name="inherit_id" ref="product.product_template_form_view"/>
<field name="arch" type="xml">
<xpath expr="//field[@name='seller_ids']" position="replace">
<field name="seller_ids"
context="{'default_product_tmpl_id': id, 'list_view_ref': 'your_module.custom_supplierinfo_tree_view_with_vendor_stock'}"
nolabel="1"
invisible="product_variant_count > 1"
readonly="product_variant_count > 1"
/>
</xpath>
</field>
</record>
but field is not showing

Source looks fine. What are your manifest and init files and what is your folder structure looking?