feat: Force _rev for queries with .select fields

This commit is a copy of #1517 applied to CozyPouchLink

When specifying fields in a query, e.g.
`Q('io.cozy.todos').where({done: true}).select(['date'])`, the revision
was missing if not explicitly given. This is now problematic because we
rely on the revision existence to identify "virtual" documents, i.e. not
persisted in CouchDB, that never have any revision.
See #1486 for more insights.

packages/cozy-pouch-link/src/CozyPouchLink.js

@@ -564,9 +564,9 @@ class PouchLink extends CozyLink {
       const findOpts = {
         sort,
         selector: findSelector,
-        // same selector as Document Collection. We force _id.
-        // Fix https://github.com/cozy/cozy-client/issues/985
-        fields: fields ? [...fields, '_id', '_type', 'class'] : undefined,
+        // same selector as Document Collection.
+        // _id is necessary for the store, and _rev is required for offline. See https://github.com/cozy/cozy-client/blob/95978d39546023920b0c01d689fed5dd41577a02/packages/cozy-client/src/CozyClient.js#L1153
+        fields: fields ? [...fields, '_id', '_rev'] : undefined,
         limit,
         skip
       }

packages/cozy-pouch-link/src/CozyPouchLink.spec.js

@@ -313,7 +313,7 @@ describe('CozyPouchLink', () => {
       expect(find).toHaveBeenLastCalledWith(
         expect.anything(),
         expect.objectContaining({
-          fields: ['label', 'done', '_id', '_type', 'class']
+          fields: ['label', 'done', '_id', '_rev']
         })
       )
     })