Remove `atob` polyfill (#9000)

* remove atob polyfill

* remove base64-js as a dependency

package.json

···
     "array.prototype.findlast": "^1.2.3",
     "await-lock": "^2.2.2",
     "babel-plugin-transform-remove-console": "^6.9.4",
-    "base64-js": "^1.5.1",
     "bcp-47": "^2.1.0",
     "bcp-47-match": "^2.0.3",
     "date-fns": "^2.30.0",

src/platform/polyfills.ts

···
 import 'react-native-url-polyfill/auto'
 import 'fast-text-encoding'
 export {}
-
-/**
-https://github.com/MaxArt2501/base64-js
-The MIT License (MIT)
-Copyright (c) 2014 MaxArt2501
- */
-
-const b64 = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/='
-// Regular expression to check formal correctness of base64 encoded strings
-const b64re =
-  /^(?:[A-Za-z\d+\/]{4})*?(?:[A-Za-z\d+\/]{2}(?:==)?|[A-Za-z\d+\/]{3}=?)?$/
-
-globalThis.atob = (str: string): string => {
-  // atob can work with strings with whitespaces, even inside the encoded part,
-  // but only \t, \n, \f, \r and ' ', which can be stripped.
-  str = String(str).replace(/[\t\n\f\r ]+/g, '')
-  if (!b64re.test(str)) {
-    throw new TypeError(
-      "Failed to execute 'atob' on 'Window': The string to be decoded is not correctly encoded.",
-    )
-  }
-
-  // Adding the padding if missing, for simplicity
-  str += '=='.slice(2 - (str.length & 3))
-  var bitmap,
-    result = '',
-    r1,
-    r2,
-    i = 0
-  for (; i < str.length; ) {
-    bitmap =
-      (b64.indexOf(str.charAt(i++)) << 18) |
-      (b64.indexOf(str.charAt(i++)) << 12) |
-      ((r1 = b64.indexOf(str.charAt(i++))) << 6) |
-      (r2 = b64.indexOf(str.charAt(i++)))
-
-    result +=
-      r1 === 64
-        ? String.fromCharCode((bitmap >> 16) & 255)
-        : r2 === 64
-          ? String.fromCharCode((bitmap >> 16) & 255, (bitmap >> 8) & 255)
-          : String.fromCharCode(
-              (bitmap >> 16) & 255,
-              (bitmap >> 8) & 255,
-              bitmap & 255,
-            )
-  }
-  return result
-}