Create a shell for `EmbeddedPaymentElement`.

[jaynewstrom-stripe]

Summary

There is no functionality added (hence no tests). We will start following up with functionality for configuration/loading. Confirm APIs are completely missing, those need more thought, and are coming later. These are all annotated with @RestrictTo, and are not publicly available. Once in private beta, we will retain the @ExperimentalEmbeddedPaymentElementApi but remove the @RestrictTo.

This hasn't gone through API review yet, but this will go through API review before we move to private beta.

Motivation

https://jira.corp.stripe.com/browse/MOBILESDK-2618

[github-actions[bot]]

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 │ 301.8 KiB │ 301.8 KiB │   0 B │ 455.5 KiB │ 455.5 KiB │  0 B 
   native │   6.2 MiB │   6.2 MiB │   0 B │  15.8 MiB │  15.8 MiB │  0 B 
    asset │   7.1 KiB │   7.1 KiB │   0 B │   6.9 KiB │   6.9 KiB │  0 B 
    other │  90.2 KiB │  90.3 KiB │ +13 B │ 170.3 KiB │ 170.3 KiB │  0 B 
──────────┼───────────┼───────────┼───────┼───────────┼───────────┼──────
    total │   9.6 MiB │   9.6 MiB │ +13 B │  21.5 MiB │  21.5 MiB │  0 B 

 DEX     │ old   │ new   │ diff      
─────────┼───────┼───────┼───────────
   files │     1 │     1 │ 0         
 strings │ 19992 │ 19992 │ 0 (+0 -0) 
   types │  6203 │  6203 │ 0 (+0 -0) 
 classes │  4994 │  4994 │ 0 (+0 -0) 
 methods │ 29803 │ 29803 │ 0 (+0 -0) 
  fields │ 17570 │ 17570 │ 0 (+0 -0) 

 ARSC    │ old  │ new  │ diff 
─────────┼──────┼──────┼──────
 configs │  164 │  164 │  0   
 entries │ 3622 │ 3622 │  0

APK

``` compressed │ uncompressed │ ──────────┬───────┼──────────┬──────┤ size │ diff │ size │ diff │ path ──────────┼───────┼──────────┼──────┼──────────────────────── 28.5 KiB │ +12 B │ 62.9 KiB │ 0 B │ ∆ META-INF/CERT.SF 1.2 KiB │ +3 B │ 1.2 KiB │ 0 B │ ∆ META-INF/CERT.RSA 25.3 KiB │ -2 B │ 62.8 KiB │ 0 B │ ∆ META-INF/MANIFEST.MF ──────────┼───────┼──────────┼──────┼──────────────────────── 54.9 KiB │ +13 B │ 127 KiB │ 0 B │ (total) ```