feat(platform-server): add API to render Module and ModuleFactory to string (#14381)

- PlatformState provides an interface to serialize the current Platform State as a string or Document.

- renderModule and renderModuleFactory are convenience methods to wait for Angular Application to stabilize and then render the state to a string.

- refactor code to remove defaultDoc from DomAdapter and inject DOCUMENT where it's needed.

modules/@angular/core/test/dom/dom_adapter_spec.ts

@@ -12,6 +12,11 @@ import {el, stringifyElement} from '@angular/platform-browser/testing/browser_ut
 
 export function main() {
   describe('dom adapter', () => {
+    let defaultDoc: any;
+    beforeEach(() => {
+      defaultDoc = getDOM().supportsDOMEvents() ? document : getDOM().createHtmlDocument();
+    });
+
     it('should not coalesque text nodes', () => {
       const el1 = el('<div>a</div>');
       const el2 = el('<div>b</div>');
@@ -68,15 +73,15 @@ export function main() {
         beforeEach(() => getDOM().resetBaseElement());
 
         it('should return null if base element is absent',
-           () => { expect(getDOM().getBaseHref()).toBeNull(); });
+           () => { expect(getDOM().getBaseHref(defaultDoc)).toBeNull(); });
 
         it('should return the value of the base element', () => {
           const baseEl = getDOM().createElement('base');
           getDOM().setAttribute(baseEl, 'href', '/drop/bass/connon/');
-          const headEl = getDOM().defaultDoc().head;
+          const headEl = defaultDoc.head;
           getDOM().appendChild(headEl, baseEl);
 
-          const baseHref = getDOM().getBaseHref();
+          const baseHref = getDOM().getBaseHref(defaultDoc);
           getDOM().removeChild(headEl, baseEl);
           getDOM().resetBaseElement();
 
@@ -86,10 +91,10 @@ export function main() {
         it('should return a relative url', () => {
           const baseEl = getDOM().createElement('base');
           getDOM().setAttribute(baseEl, 'href', 'base');
-          const headEl = getDOM().defaultDoc().head;
+          const headEl = defaultDoc.head;
           getDOM().appendChild(headEl, baseEl);
 
-          const baseHref = getDOM().getBaseHref();
+          const baseHref = getDOM().getBaseHref(defaultDoc);
           getDOM().removeChild(headEl, baseEl);
           getDOM().resetBaseElement();