Add fragment handling to stripecardscan and update READMEs

[awush-stripe]

Summary

Add the ability to launch cardscan and cardimageverification from fragments
Update the readme with an example for cardscan

Motivation

DoorDash needs to launch CIV from a fragment. Additionally, we needed an example for card scan in the README.

Testing

• Added tests
• Modified tests
• Manually verified

Changelog

[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 │  12.1 MiB │  12.1 MiB │  0 B │  41.1 MiB │  41.1 MiB │  0 B 
     arsc │   1.6 MiB │   1.6 MiB │  0 B │   1.6 MiB │   1.6 MiB │  0 B 
 manifest │   2.7 KiB │   2.7 KiB │  0 B │  11.1 KiB │  11.1 KiB │  0 B 
      res │ 697.8 KiB │ 697.8 KiB │  0 B │   1.1 MiB │   1.1 MiB │  0 B 
    asset │    78 KiB │    78 KiB │  0 B │ 109.5 KiB │ 109.5 KiB │  0 B 
    other │  78.7 KiB │  78.7 KiB │  0 B │ 154.6 KiB │ 154.6 KiB │  0 B 
──────────┼───────────┼───────────┼──────┼───────────┼───────────┼──────
    total │  14.5 MiB │  14.5 MiB │  0 B │    44 MiB │    44 MiB │  0 B 

         │          raw           │           unique            
         ├────────┬────────┬──────┼────────┬────────┬───────────
 DEX     │ old    │ new    │ diff │ old    │ new    │ diff      
─────────┼────────┼────────┼──────┼────────┼────────┼───────────
   files │      3 │      3 │    0 │        │        │           
 strings │ 192300 │ 192300 │    0 │ 173994 │ 173994 │ 0 (+0 -0) 
   types │  33441 │  33441 │    0 │  31640 │  31640 │ 0 (+0 -0) 
 classes │  29230 │  29230 │    0 │  29230 │  29230 │ 0 (+0 -0) 
 methods │ 168303 │ 168303 │    0 │ 163678 │ 163678 │ 0 (+0 -0) 
  fields │ 123202 │ 123202 │    0 │ 122734 │ 122734 │ 0 (+0 -0) 

 ARSC    │ old  │ new  │ diff 
─────────┼──────┼──────┼──────
 configs │  298 │  298 │  0   
 entries │ 5394 │ 5394 │  0