[IMP] mail: convert LegacyComponent webClientViewAttachmentView

Since
https://github.com/odoo/enterprise/commit/afcdd1878a2eaf4cbca85d1169dea31a108c8c43#diff-f064a21c91b8daa5d78c44e88e2c02345ff0a7230403dd3600a65d3a6b0653d3L18
there is no listener for preview_attachment_validation.

Part of task-2783065

closes odoo/odoo#102406

Signed-off-by: Sébastien Theys (seb) <seb@odoo.com>

addons/mail/static/src/components/web_client_view_attachment_view/web_client_view_attachment_view.js

@@ -1,18 +1,16 @@
 /** @odoo-module **/
 
-import { useComponentToModel } from '@mail/component_hooks/use_component_to_model';
 import { useRefToModel } from '@mail/component_hooks/use_ref_to_model';
 import { useUpdateToModel } from '@mail/component_hooks/use_update_to_model';
 import { registerMessagingComponent } from '@mail/utils/messaging_component';
 
-import { LegacyComponent } from '@web/legacy/legacy_component';
+const { Component } = owl;
 
-export class WebClientViewAttachmentView extends LegacyComponent {
+export class WebClientViewAttachmentView extends Component {
     /**
      * @override
      */
     setup() {
-        useComponentToModel({ fieldName: 'component' });
         useRefToModel({ fieldName: 'iframeViewerPdfRef', refName: 'iframeViewerPdf' });
         useUpdateToModel({ methodName: 'onComponentUpdate' });
     }

addons/mail/static/src/models/web_client_view_attachment_view.js

@@ -28,7 +28,6 @@ registerModel({
             if (this.iframeViewerPdfRef.el) {
                 hidePDFJSButtons(this.iframeViewerPdfRef.el);
             }
-            this.component.trigger('preview_attachment_validation');
         },
         async setMainAttachmentFromIndex(index) {
             await this.thread.setMainAttachment(this.thread.attachmentsInWebClientView[index]);
@@ -48,7 +47,6 @@ registerModel({
         },
     },
     fields: {
-        component: attr(),
         id: attr({
             identifying: true,
         }),