Remove instantDebitsBillingDetails feature flag

[tillh-stripe]

Summary

This pull request removes the instantDebitsBillingDetails feature flag, as we successfully bug-bashed this.

Motivation

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 │   3.8 MiB │   3.8 MiB │ -20 B │   8.4 MiB │   8.4 MiB │ +356 B 
     arsc │   2.3 MiB │   2.3 MiB │   0 B │   2.3 MiB │   2.3 MiB │    0 B 
 manifest │     5 KiB │     5 KiB │   0 B │  24.9 KiB │  24.9 KiB │    0 B 
      res │ 902.3 KiB │ 902.3 KiB │   0 B │   1.4 MiB │   1.4 MiB │    0 B 
   native │   2.6 MiB │   2.6 MiB │   0 B │     6 MiB │     6 MiB │    0 B 
    asset │   1.6 MiB │   1.6 MiB │  -1 B │   1.6 MiB │   1.6 MiB │   -1 B 
    other │ 199.8 KiB │ 199.8 KiB │  -7 B │ 440.1 KiB │ 440.1 KiB │    0 B 
──────────┼───────────┼───────────┼───────┼───────────┼───────────┼────────
    total │  11.4 MiB │  11.4 MiB │ -28 B │  20.2 MiB │  20.2 MiB │ +355 B 

 DEX     │ old   │ new   │ diff         
─────────┼───────┼───────┼──────────────
   files │     1 │     1 │  0           
 strings │ 39765 │ 39764 │ -1 (+1 -2)   
   types │ 13713 │ 13713 │  0 (+0 -0)   
 classes │ 11405 │ 11405 │  0 (+0 -0)   
 methods │ 58617 │ 58617 │  0 (+0 -0)   
  fields │ 38905 │ 38909 │ +4 (+20 -16) 

 ARSC    │ old  │ new  │ diff 
─────────┼──────┼──────┼──────
 configs │  242 │  242 │  0   
 entries │ 6190 │ 6190 │  0

APK

    compressed    │    uncompressed    │                                           
──────────┬───────┼───────────┬────────┤                                           
 size     │ diff  │ size      │ diff   │ path                                      
──────────┼───────┼───────────┼────────┼───────────────────────────────────────────
  3.8 MiB │ -20 B │   8.4 MiB │ +356 B │ ∆ classes.dex                             
   53 KiB │  -8 B │ 117.6 KiB │    0 B │ ∆ META-INF/CERT.SF                        
    272 B │  +1 B │     120 B │    0 B │ ∆ META-INF/version-control-info.textproto 
  7.8 KiB │  -1 B │   7.7 KiB │   -1 B │ ∆ assets/dexopt/baseline.prof             
  1.2 KiB │  +1 B │   1.2 KiB │    0 B │ ∆ META-INF/CERT.RSA                       
 49.7 KiB │  -1 B │ 117.5 KiB │    0 B │ ∆ META-INF/MANIFEST.MF                    
──────────┼───────┼───────────┼────────┼───────────────────────────────────────────
    4 MiB │ -28 B │   8.6 MiB │ +355 B │ (total)

DEX

STRINGS:

   old   │ new   │ diff       
  ───────┼───────┼────────────
   39765 │ 39764 │ -1 (+1 -2) 
  
  + ~~R8{"backend":"dex","compilation-mode":"release","has-checksums":false,"min-api":21,"pg-map-id":"a40ed67","r8-mode":"full","version":"8.7.14"}
  
  - IBP Billing Details
  - ~~R8{"backend":"dex","compilation-mode":"release","has-checksums":false,"min-api":21,"pg-map-id":"0b9e3a6","r8-mode":"full","version":"8.7.14"}
  

FIELDS:

   old   │ new   │ diff         
  ───────┼───────┼──────────────
   38905 │ 38909 │ +4 (+20 -16) 
  
  + D7.L A: c
  + D7.L B: c
  + D7.L C: c
  + D7.L D: g
  + D7.L j: boolean
  + D7.L k: boolean
  + D7.L l: boolean
  + D7.L m: boolean
  + D7.L n: p1
  + D7.L p: p1
  + D7.L q: c
  + D7.L r: w0
  + D7.L s: c
  + D7.L t: X0
  + D7.L u: h
  + D7.L v: b0
  + D7.L w: b0
  + D7.L x: q1
  + D7.L y: d0
  + D7.L z: d0
  
  - D7.L j: p1
  - D7.L k: c
  - D7.L l: p1
  - D7.L m: c
  - D7.L n: w0
  - D7.L p: X0
  - D7.L q: h
  - D7.L r: b0
  - D7.L s: q1
  - D7.L t: d0
  - D7.L u: d0
  - D7.L v: c
  - D7.L w: c
  - D7.L x: c
  - D7.L y: g
  - g5.d d: q