refactor(ivy): use a named type for ImportManager import structures (#25445)

Previously we were using an anonymous type `{specifier: string; qualifier: string;}`
throughout the code base. This commit gives this type a name and ensures it
is only defined in one place.

PR Close #25445

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

@@ -18,6 +18,7 @@ ts_library(
         "//packages/compiler-cli/src/ngtsc/reflection",
         "//packages/compiler-cli/src/ngtsc/testing",
         "//packages/compiler-cli/src/ngtsc/transform",
+        "//packages/compiler-cli/src/ngtsc/translator",
         "//packages/compiler-cli/test:test_utils",
         "@npm//@types/convert-source-map",
         "@npm//@types/mock-fs",