core: rename queued_message → pending_reload_message
    
    This field is only used for pending Reload() replies, hence let's rename
    it to be more descriptive and precise.
    
    No change in behaviour.
    
    (cherry picked from commit 209de5256b7ba8600c3e73a85a43b86708998d65)
    
    Resolves: #1647359
    
    patch_name: 0035-core-rename-queued_message-pending_reload_message.patch
    present_in_specfile: true
    location_in_specfile: 35
    squash_commits: true