fix(ivy): ngtsc is unable to detect flat module entry-point on windows (#29453)

Currently when building an Angular project with `ngtsc`
and `flatModuleOutFile` enabled, the Ngtsc build will fail
if there are multiple source files as root file names.

Ngtsc and NGC currently determine the entry-point for multiple
root file names by looking for files ending with `/index.ts`.

This functionality is technically deprecated, but still supported
and currently breaks on Windows as the root file names are not
guaranteed to be normalized POSIX-like paths.

In order to make this logic more reliable in the future, this commit
also switches the shim generators and entry-point logic to the branded
path types. This ensures that we don't break this in the future.

PR Close #29453

packages/compiler-cli/src/ngtsc/entry_point/test/BUILD.bazel

@@ -11,6 +11,7 @@ ts_library(
     deps = [
         "//packages:types",
         "//packages/compiler-cli/src/ngtsc/entry_point",
+        "//packages/compiler-cli/src/ngtsc/path",
         "@npm//typescript",
     ],
 )

packages/compiler-cli/src/ngtsc/entry_point/test/entry_point_spec.ts

@@ -7,22 +7,23 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
+import {AbsoluteFsPath} from '../../path/src/types';
 import {findFlatIndexEntryPoint} from '../src/logic';
 
 describe('entry_point logic', () => {
 
   describe('findFlatIndexEntryPoint', () => {
 
-    it('should use the only source file if only a single one is specified',
-       () => { expect(findFlatIndexEntryPoint(['/src/index.ts'])).toBe('/src/index.ts'); });
+    it('should use the only source file if only a single one is specified', () => {
+      expect(findFlatIndexEntryPoint([AbsoluteFsPath.fromUnchecked('/src/index.ts')]))
+          .toBe('/src/index.ts');
+    });
 
     it('should use the shortest source file ending with "index.ts" for multiple files', () => {
       expect(findFlatIndexEntryPoint([
-        '/src/deep/index.ts', '/src/index.ts', '/index.ts'
+        AbsoluteFsPath.fromUnchecked('/src/deep/index.ts'),
+        AbsoluteFsPath.fromUnchecked('/src/index.ts'), AbsoluteFsPath.fromUnchecked('/index.ts')
       ])).toBe('/index.ts');
     });
-
-    it('should normalize the path separators for the found entry point',
-       () => { expect(findFlatIndexEntryPoint(['\\src\\index.ts'])).toBe('/src/index.ts'); });
   });
 });