Add polling for Cash App Pay flow result processing

[tillh-stripe]

Summary

This pull request adds polling for Cash App Pay payments in the PaymentFlowResultProcessor to adapt to the backend changes.

(cc @porter-stripe)

Motivation

More resilient Cash App Pay payments.

Testing

• Added tests
• Modified tests
• Manually verified

Screenshots

Before	After
before screenshot	after screenshot

Changelog

[github-actions]

Diffuse output:

OLD: paymentsheet-example-release-master.apk (signature: V1, V2)
NEW: paymentsheet-example-release-pr.apk (signature: V1, V2)

          │           compressed           │         uncompressed          
          ├───────────┬───────────┬────────┼───────────┬───────────┬───────
 APK      │ old       │ new       │ diff   │ old       │ new       │ diff  
──────────┼───────────┼───────────┼────────┼───────────┼───────────┼───────
      dex │   3.4 MiB │   3.4 MiB │ +180 B │   7.4 MiB │   7.4 MiB │ +64 B 
     arsc │   2.1 MiB │   2.1 MiB │    0 B │   2.1 MiB │   2.1 MiB │   0 B 
 manifest │   4.6 KiB │   4.6 KiB │    0 B │  22.3 KiB │  22.3 KiB │   0 B 
      res │ 869.1 KiB │ 869.1 KiB │    0 B │   1.3 MiB │   1.3 MiB │   0 B 
   native │   2.6 MiB │   2.6 MiB │    0 B │     6 MiB │     6 MiB │   0 B 
    asset │     3 MiB │     3 MiB │    0 B │     3 MiB │     3 MiB │   0 B 
    other │ 199.7 KiB │ 199.7 KiB │   +1 B │ 446.8 KiB │ 446.8 KiB │   0 B 
──────────┼───────────┼───────────┼────────┼───────────┼───────────┼───────
    total │  12.1 MiB │  12.1 MiB │ +181 B │  20.3 MiB │  20.3 MiB │ +64 B 

 DEX     │ old   │ new   │ diff       
─────────┼───────┼───────┼────────────
   files │     1 │     1 │  0         
 strings │ 36239 │ 36239 │  0 (+1 -1) 
   types │ 12046 │ 12046 │  0 (+0 -0) 
 classes │ 10146 │ 10146 │  0 (+0 -0) 
 methods │ 53659 │ 53659 │  0 (+0 -0) 
  fields │ 34114 │ 34115 │ +1 (+2 -1) 

 ARSC    │ old  │ new  │ diff 
─────────┼──────┼──────┼──────
 configs │  291 │  291 │  0   
 entries │ 6942 │ 6942 │  0

APK

    compressed     │   uncompressed    │                        
──────────┬────────┼───────────┬───────┤                        
 size     │ diff   │ size      │ diff  │ path                   
──────────┼────────┼───────────┼───────┼────────────────────────
  3.4 MiB │ +180 B │   7.4 MiB │ +64 B │ ∆ classes.dex          
 48.5 KiB │   +3 B │ 140.8 KiB │   0 B │ ∆ META-INF/MANIFEST.MF 
 62.7 KiB │   -2 B │ 140.9 KiB │   0 B │ ∆ META-INF/CERT.SF     
──────────┼────────┼───────────┼───────┼────────────────────────
  3.5 MiB │ +181 B │   7.7 MiB │ +64 B │ (total)

DEX

STRINGS:

   old   │ new   │ diff      
  ───────┼───────┼───────────
   36239 │ 36239 │ 0 (+1 -1) 
  + ~~R8{backend:dex,compilation-mode:release,has-checksums:false,min-api:21,pg-map-id:d552af5,r8-mode:full,version:8.0.40}
  
  - ~~R8{backend:dex,compilation-mode:release,has-checksums:false,min-api:21,pg-map-id:dced842,r8-mode:full,version:8.0.40}
  

FIELDS:

   old   │ new   │ diff       
  ───────┼───────┼────────────
   34114 │ 34115 │ +1 (+2 -1) 
  + hc.m2 w: m2
  + hc.m2 x: m2[]
  
  - hc.m2 w: m2[]