Handle blank fields in ShippingInfoWidget

[brnunes-stripe]

Summary

Treat blank fields as invalid in ShippingInfoWidget.
Previously only fully empty fields were considered invalid.

Motivation

#5690

Testing

• Added tests
• Modified tests
• Manually verified

[github-actions]

Diffuse output:

OLD: paymentsheet-example-release-master.apk (signature: none)
NEW: paymentsheet-example-release-pr.apk (signature: none)

          │         compressed          │         uncompressed          
          ├──────────┬──────────┬───────┼───────────┬───────────┬───────
 APK      │ old      │ new      │ diff  │ old       │ new       │ diff  
──────────┼──────────┼──────────┼───────┼───────────┼───────────┼───────
      dex │  5.2 MiB │  5.2 MiB │ +80 B │  13.5 MiB │  13.5 MiB │ -60 B 
     arsc │  1.9 MiB │  1.9 MiB │   0 B │   1.9 MiB │   1.9 MiB │   0 B 
 manifest │  4.1 KiB │  4.1 KiB │   0 B │  19.2 KiB │  19.2 KiB │   0 B 
      res │    1 MiB │    1 MiB │   0 B │   1.8 MiB │   1.8 MiB │   0 B 
   native │  2.5 MiB │  2.5 MiB │   0 B │   5.9 MiB │   5.9 MiB │   0 B 
    asset │    3 MiB │    3 MiB │   0 B │     3 MiB │     3 MiB │   0 B 
    other │ 82.5 KiB │ 82.5 KiB │   0 B │ 158.5 KiB │ 158.5 KiB │   0 B 
──────────┼──────────┼──────────┼───────┼───────────┼───────────┼───────
    total │ 13.7 MiB │ 13.7 MiB │ +80 B │  26.2 MiB │  26.2 MiB │ -60 B 

         │          raw           │           unique            
         ├────────┬────────┬──────┼────────┬────────┬───────────
 DEX     │ old    │ new    │ diff │ old    │ new    │ diff      
─────────┼────────┼────────┼──────┼────────┼────────┼───────────
   files │      2 │      2 │    0 │        │        │           
 strings │  84264 │  84264 │    0 │  69878 │  69878 │ 0 (+0 -0) 
   types │  21729 │  21729 │    0 │  19447 │  19447 │ 0 (+0 -0) 
 classes │  17424 │  17424 │    0 │  17424 │  17424 │ 0 (+0 -0) 
 methods │  93712 │  93712 │    0 │  89501 │  89501 │ 0 (+0 -0) 
  fields │ 101770 │ 101770 │    0 │ 100426 │ 100426 │ 0 (+0 -0) 

 ARSC    │ old  │ new  │ diff 
─────────┼──────┼──────┼──────
 configs │  334 │  334 │  0   
 entries │ 6246 │ 6246 │  0

APK

   compressed    │  uncompressed   │                
─────────┬───────┼─────────┬───────┤                
 size    │ diff  │ size    │ diff  │ path           
─────────┼───────┼─────────┼───────┼────────────────
 2.1 MiB │ +80 B │ 5.7 MiB │ -60 B │ ∆ classes2.dex 
─────────┼───────┼─────────┼───────┼────────────────
 2.1 MiB │ +80 B │ 5.7 MiB │ -60 B │ (total)