refactor(compiler-cli): expose loadTestDirectory() test helper (#36843)

This helper can be useful in other packages to load files from the
real disk into a mock file system.

PR Close #36843

packages/compiler-cli/test/helpers/BUILD.bazel

@@ -8,6 +8,7 @@ ts_library(
     srcs = glob([
         "**/*.ts",
     ]),
+    module_name = "@angular/compiler-cli/test/helpers",
     deps = [
         "//packages:types",
         "//packages/compiler-cli/src/ngtsc/file_system",