[19.0][MIG] server_action_mass_edit_onchange: Migration to 19.0

[MohamedOsman7]

Migration of server_action_mass_edit_onchange from 18.0 to 19.0

This PR migrates the module to 19.0. The module extends server_action_mass_edit to optionally play a field's onchange methods before writing the value during a mass edit.

Changes

• Version bumped to 19.0.1.0.0.
• No functional/code changes needed — the model, wizard and view extension
  points are still compatible with 19.0:
  • mass.editing.wizard._exec_write() override still matches the base signature.
  • The inherited view anchor server_action_mass_edit.view_server_action_form and the apply_domain field it attaches to still exist.
  • play_onchanges() is still provided by onchange_helper (server-tools).
• Tests adapted to 19.0 API changes in res.partner:
  • Partner class was renamed to ResPartner.
  • email no longer has an onchange method. The negative test case (a field with apply_onchanges=False must not trigger its onchange) now uses company_type / onchange_company_type instead of email / onchange_email, preserving the original test intent.

Testing

• TestMassEditingWithOnChange.test_wizard_field_onchange passes on 19.0 (verified locally, 0 failed, 0 error(s)).

[MohamedOsman7]

@trisdoan can you please make a review?