fix: replace JS window.open with links - EXO-89155

[ahamdi]

Why is this change needed?

Prior to this change, opening a document for editing/viewing (and a handful of other document actions — WebDAV drive links, folder navigation, newly-created attachments) called window.open(url, target) directly across the Documents webapp. Direct window.open calls bypass native browser link semantics (no hover preview, no right-click "open in new tab", no middle-click support) and, in one path (EditMenuAction.vue / OpenReadOnlyMenuAction.vue), were reported to pop the editor in a separate browser window instead of a tab depending on browser settings.

How does it address the issue?

This change replaces every window.open call in documents-webapp with real -based navigation:

• Adds a shared openLink(url, target = '_blank') helper to js/DocumentsUtils.js (exposed as this.$documentsUtils.openLink), used as a drop-in replacement for window.open(url, target) everywhere the target URL is only known inside a dispatcher method (folder vs. file, sometimes after an async fetch). It also correctly handles target: '_self' as an in-place window.location.href navigation rather than a popped window.
• Extends DocumentActionItem.vue (the shared document context-menu item) with optional href/target props, backward-compatible with every existing non-link action.
• Converts EditMenuAction.vue and OpenReadOnlyMenuAction.vue — the primary "Edit"/"Open read-only" entries — to real links via computed editLink/readOnlyLink properties, replacing their window.open click handlers.
• Mechanically swaps the remaining 13 call sites (attachment/main.js, documents/main.js, document-gadget/main.js, DocumentsFileNameCell.vue, FileSearchCard.vue, DocumentListDrawer.vue, DocumentsMain.vue, DocumentInfoDrawer.vue, and 4 attachment components) to this.$documentsUtils.openLink(...).

No functional/URL-building logic changed — only how the resulting URL is navigated to.

Knowledge: none — mechanical window.open → conversion using the addon's existing DocumentsUtils helper pattern, no new architecture or extension point introduced.