fix(ivy): support multiple directives with the same selector (#27298)

Previously the concept of multiple directives with the same selector was
not supported by ngtsc. This is due to the treatment of directives for a
component as a Map from selector to the directive, which is an erroneous
representation.

Now the directives for a component are stored as an array which supports
multiple directives with the same selector.

Testing strategy: a new ngtsc_spec test asserts that multiple directives
with the same selector are matched on an element.

PR Close #27298

packages/compiler-cli/test/ngtsc/ngtsc_spec.ts

@@ -832,4 +832,31 @@ describe('ngtsc behavioral tests', () => {
     expect(jsContents).toContain('ɵsetClassMetadata(TestNgModule, ');
     expect(jsContents).toContain('ɵsetClassMetadata(TestPipe, ');
   });
+
+  it('should compile a template using multiple directives with the same selector', () => {
+    env.tsconfig();
+    env.write('test.ts', `
+      import {Component, Directive, NgModule} from '@angular/core';
+
+      @Directive({selector: '[test]'})
+      class DirA {}
+
+      @Directive({selector: '[test]'})
+      class DirB {}
+
+      @Component({
+        template: '<div test></div>',
+      })
+      class Cmp {}
+
+      @NgModule({
+        declarations: [Cmp, DirA, DirB],
+      })
+      class Module {}
+    `);
+
+    env.driveMain();
+    const jsContents = env.getContents('test.js');
+    expect(jsContents).toMatch(/directives: \[DirA,\s+DirB\]/);
+  });
 });