feat(core): template-var-assignment update schematic (#29608)

Introduces a new update schematic called "template-var-assignment"
that is responsible for analyzing template files in order to warn
developers if template variables are assigned to values.

The schematic also comes with a driver for `tslint` so that the
check can be used wtihin Google.

PR Close #29608

packages/core/schematics/migrations/template-var-assignment/BUILD.bazel

@@ -0,0 +1,19 @@
+load("//tools:defaults.bzl", "ts_library")
+
+ts_library(
+    name = "template-var-assignment",
+    srcs = glob(["**/*.ts"]),
+    tsconfig = "//packages/core/schematics:tsconfig.json",
+    visibility = [
+        "//packages/core/schematics:__pkg__",
+        "//packages/core/schematics/migrations/template-var-assignment/google3:__pkg__",
+        "//packages/core/schematics/test:__pkg__",
+    ],
+    deps = [
+        "//packages/compiler",
+        "//packages/core/schematics/utils",
+        "@npm//@angular-devkit/schematics",
+        "@npm//@types/node",
+        "@npm//typescript",
+    ],
+)