As part of FW-1265, the `@angular/core` package is made compatible
with the TypeScript `--strict` flag. This already unveiled a few bugs,
so the strictness flag seems to help with increasing the overall code health.
Read more about the strict flag [here](https://www.typescriptlang.org/docs/handbook/compiler-options.html)
PR Close#30993
The API changes are due to enabling strict checks in TypeScript (via `strict: true`).
The payload size changes in `polyfills.js` are due to more browser APIs being patched in recent versions (e.g. `fetch`, `customElement v1`).
PR Close#28219
