[MOBILESDK-2894] [Android] Make Default Payment Method selected

[tianzhao-stripe]

Summary

Added Logic for retrieving the initial payment selection
did some refactoring in DefaultPaymentElementLoaderTest to accomodate testing for selection

Motivation

https://jira.corp.stripe.com/browse/MOBILESDK-2894

Testing

• Added tests
• Modified tests
• Manually verified

Screenshots

	Before	After
Vertical Mode
Horizontal Mode

Changelog

N.A.

[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 │   4.1 MiB │   4.1 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 KiB │     8 KiB │  0 B 
      res │ 302.6 KiB │ 302.6 KiB │  0 B │ 456.7 KiB │ 456.7 KiB │  0 B 
   native │   6.2 MiB │   6.2 MiB │  0 B │  15.8 MiB │  15.8 MiB │  0 B 
    asset │   7.2 KiB │   7.2 KiB │  0 B │   6.9 KiB │   6.9 KiB │  0 B 
    other │  90.4 KiB │  90.4 KiB │ -2 B │ 170.7 KiB │ 170.7 KiB │  0 B 
──────────┼───────────┼───────────┼──────┼───────────┼───────────┼──────
    total │   9.6 MiB │   9.6 MiB │ -2 B │  21.5 MiB │  21.5 MiB │  0 B 

 DEX     │ old   │ new   │ diff      
─────────┼───────┼───────┼───────────
   files │     1 │     1 │ 0         
 strings │ 19982 │ 19982 │ 0 (+0 -0) 
   types │  6194 │  6194 │ 0 (+0 -0) 
 classes │  4985 │  4985 │ 0 (+0 -0) 
 methods │ 29820 │ 29820 │ 0 (+0 -0) 
  fields │ 17539 │ 17539 │ 0 (+0 -0) 

 ARSC    │ old  │ new  │ diff 
─────────┼──────┼──────┼──────
 configs │  164 │  164 │  0   
 entries │ 3624 │ 3624 │  0

APK

   compressed    │   uncompressed   │                        
──────────┬──────┼───────────┬──────┤                        
 size     │ diff │ size      │ diff │ path                   
──────────┼──────┼───────────┼──────┼────────────────────────
 25.4 KiB │ -3 B │    63 KiB │  0 B │ ∆ META-INF/MANIFEST.MF 
 28.5 KiB │ +2 B │  63.1 KiB │  0 B │ ∆ META-INF/CERT.SF     
  1.2 KiB │ -1 B │   1.2 KiB │  0 B │ ∆ META-INF/CERT.RSA    
──────────┼──────┼───────────┼──────┼────────────────────────
 55.1 KiB │ -2 B │ 127.3 KiB │  0 B │ (total)