add R-level message translation to FR

[cregouby]

and turn messages to be consistently managed by {glue}.

==> devtools::test()

ℹ Testing torchvision
✔ | F W  S  OK | Context
✔ |         21 | dataset-cifar [13.9s]                            
✔ |         26 | dataset-mnist [22.5s]                            
✔ |         74 | folder-dataset                                   
✔ |          3 | message-translations                             
✔ |          6 | models-alexnet [1.0s]                            
✔ |          4 | models-inception                                 
✔ |         13 | models-mobilenetv2 [1.8s]                        
✔ |         80 | models-resnet [19.2s]                            
✔ |         48 | models-vgg [25.1s]                               
✔ |          6 | transforms-defaults                              
✔ |      1   0 | transforms-magick                                
✔ |      1  57 | transforms                                       
✔ |         34 | vision-utils                                     

══ Results ═══════════════════════════════════════════════════════
Duration: 86.1 s

── Skipped tests (2) ─────────────────────────────────────────────
• empty test (1): test-transforms-magick.R:1:1
• not implemented (1): test-transforms.R:97:3

[ FAIL 0 | WARN 0 | SKIP 2 | PASS 372 ]

MMH - cool code.