Update external payment methods playground setting to use enum of options

[amk-stripe]

Summary

Update external payment methods playground setting to use enum of options

Motivation

• Make it easier and less error prone to test EPMs during the bug bash and going forward.
• Consistency with iOS

The one downside that I see to this approach is that it's now harder to test just one specific EPM. But we can mitigate this by selecting "All" and then using payment method order to make the EPM we're interested in testing show up early in the list.

Testing

• Added tests
• Modified tests
• Manually verified

[github-actions]

Diffuse output:

OLD: identity-example-release-base.apk (signature: V1, V2)
NEW: identity-example-release-pr.apk (signature: V1, V2)

          │          compressed          │         uncompressed         
          ├───────────┬───────────┬──────┼───────────┬───────────┬──────
 APK      │ old       │ new       │ diff │ old       │ new       │ diff 
──────────┼───────────┼───────────┼──────┼───────────┼───────────┼──────
      dex │     2 MiB │     2 MiB │  0 B │   4.3 MiB │   4.3 MiB │  0 B 
     arsc │     1 MiB │     1 MiB │  0 B │     1 MiB │     1 MiB │  0 B 
 manifest │   2.3 KiB │   2.3 KiB │  0 B │   8.1 KiB │   8.1 KiB │  0 B 
      res │ 301.5 KiB │ 301.5 KiB │  0 B │   455 KiB │   455 KiB │  0 B 
   native │   7.3 MiB │   7.3 MiB │  0 B │  18.4 MiB │  18.4 MiB │  0 B 
    asset │   1.5 MiB │   1.5 MiB │  0 B │   1.5 MiB │   1.5 MiB │  0 B 
    other │    87 KiB │    87 KiB │ -4 B │ 161.5 KiB │ 161.5 KiB │  0 B 
──────────┼───────────┼───────────┼──────┼───────────┼───────────┼──────
    total │  12.2 MiB │  12.2 MiB │ -4 B │  25.8 MiB │  25.8 MiB │  0 B 

 DEX     │ old   │ new   │ diff      
─────────┼───────┼───────┼───────────
   files │     1 │     1 │ 0         
 strings │ 21686 │ 21686 │ 0 (+0 -0) 
   types │  6869 │  6869 │ 0 (+0 -0) 
 classes │  5634 │  5634 │ 0 (+0 -0) 
 methods │ 31447 │ 31447 │ 0 (+0 -0) 
  fields │ 18315 │ 18315 │ 0 (+0 -0) 

 ARSC    │ old  │ new  │ diff 
─────────┼──────┼──────┼──────
 configs │  164 │  164 │  0   
 entries │ 3404 │ 3404 │  0

APK

   compressed    │   uncompressed   │                                           
──────────┬──────┼───────────┬──────┤                                           
 size     │ diff │ size      │ diff │ path                                      
──────────┼──────┼───────────┼──────┼───────────────────────────────────────────
 29.1 KiB │ -5 B │    64 KiB │  0 B │ ∆ META-INF/CERT.SF                        
  1.2 KiB │ +2 B │   1.2 KiB │  0 B │ ∆ META-INF/CERT.RSA                       
 25.9 KiB │ -2 B │  63.9 KiB │  0 B │ ∆ META-INF/MANIFEST.MF                    
    272 B │ +1 B │     120 B │  0 B │ ∆ META-INF/version-control-info.textproto 
──────────┼──────┼───────────┼──────┼───────────────────────────────────────────
 56.4 KiB │ -4 B │ 129.2 KiB │  0 B │ (total)