[19.0][MIG] web_widget_x2many_2d_matrix: Migration to 19.0

[ferran-S73]

Migration from #3310

[alexey-pelykh]

Thanks for picking up this migration, @ferran-S73!

I maintain this module, so I went through the changes carefully. The many2one tuple-to-object migration (value[0] → value.id, value[1] → value.display_name) and the users → user_ids rename in the demo view are both correct for 19.0. Manifest version bump looks good too.

However, I have one concern that I believe needs to be addressed before merging:

Renderer setup: onWillUpdateProps vs onWillRender

The 18.0 version uses onWillRender to recalculate columns, rows, and matrix on every render cycle. The 19.0 PR replaces this with setup() + onWillUpdateProps. The problem is that onWillUpdateProps only fires when the parent passes new props — it does not fire when the user edits a value cell inline. Inline edits mutate the records within this.props.list without the parent re-passing props to the renderer, so the matrix/totals would not update.

The 18.0 branch includes a test that validates exactly this scenario ("matrix totals are updated correctly after several edits"), which was dropped in this PR. I suspect the test was removed because it fails with the current onWillUpdateProps approach.

Suggested fix: keep using onWillRender as in 18.0 — it's still available in OWL 3 and correctly handles all reactivity scenarios:

setup() {
    onWillRender(() => {
        const records = this.list.records;
        this.columns = this._getColumns(records);
        this.rows = this._getRows(records);
        this.matrix = this._getMatrix(records);
    });
}

And please restore the dropped test from 18.0 as well:

test("matrix totals are updated correctly after several edits", async () => { ... });

(along with the contains and queryAll imports it needs).

Everything else looks clean — nice work on the migration overall.