Replace i18n generation script with something matching our project

We've been relying on flow being close enough to TypeScript for so long that it is starting to run into issues. Here we switch to babel's parser given we already use babel in the project.

Babel's parser is also *slightly* faster, allowing us to generate strings 0.1s faster.

package.json

@@ -105,6 +105,7 @@
   "devDependencies": {
     "@babel/cli": "^7.10.5",
     "@babel/core": "^7.10.5",
+    "@babel/parser": "^7.11.0",
     "@babel/plugin-proposal-class-properties": "^7.10.4",
     "@babel/plugin-proposal-decorators": "^7.10.5",
     "@babel/plugin-proposal-export-default-from": "^7.10.4",
@@ -117,6 +118,7 @@
     "@babel/preset-react": "^7.10.4",
     "@babel/preset-typescript": "^7.10.4",
     "@babel/register": "^7.10.5",
+    "@babel/traverse": "^7.11.0",
     "@peculiar/webcrypto": "^1.1.2",
     "@types/classnames": "^2.2.10",
     "@types/counterpart": "^0.18.1",
@@ -145,9 +147,7 @@
     "eslint-plugin-flowtype": "^2.50.3",
     "eslint-plugin-react": "^7.20.3",
     "eslint-plugin-react-hooks": "^2.5.1",
-    "estree-walker": "^0.9.0",
     "file-loader": "^3.0.1",
-    "flow-parser": "0.57.3",
     "glob": "^5.0.15",
     "jest": "^24.9.0",
     "jest-canvas-mock": "^2.2.0",