Large remote shares get synced by default when its size is "Pending"

[SamuAlfageme]

Yet another issue explained by the mighty @cdamken. I believe it's quite related to fed. shares performance (ref. https://github.com/owncloud/enterprise/issues/2512) - but a client workaround might be also in place.

Steps to reproduce

Having the "Ask for confirmation before synchronizing folders larger than 500MB" setting enabled:

1. Create a folder that contains large subfolders (> 500MB) on ownCloud instance "A"
2. Sync a user on a remote instance "B"
3. Share the folder in "A" with user@B (remote)
4. Accept the share in the client -> size on the folder's PROPFIND might be "pending"

Expected behavior

Since individual sizes on sub-folders are available but total root size is not; the client could wait for the full remote discovery to be carried out and calculate its own "full virtual tree size" to determine whether these kind of conditions might met

Actual behavior

• The accepted fed. share is included on the "selective sync list" by default (as designed*) and therefore:
• The large subfolders appear on the "Confirmation area" (account's bottom part) one by one, stacking instead of getting just one confirmation for the container folder.

*: would it be interesting to introduce a new "do not sync (remote) shares by default" as we do for mounted storages? (#5340) -> rel. to #6378 cc/ @hodyroff @pmaier1

[TheOneRing]

Removed in #11517