refactor(core): ensure compatibility with typescript strict flag (#30993)

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

packages/BUILD.bazel

@@ -23,6 +23,12 @@ ts_config(
     deps = [":tsconfig-build.json"],
 )
 
+ts_config(
+    name = "tsconfig-build-no-strict",
+    src = "tsconfig-build-no-strict.json",
+    deps = [":tsconfig-build.json"],
+)
+
 exports_files([
     "license-banner.txt",
     "README.md",