fix: public api surface fixes + stability markers

- ts-api-guardian will now error if a new public symbol is added with a stability marker (`@stable`, `@experimental`, `@deprecated`)
- DomEventsPlugin and KeyEventsPlugin were removed from public api surface - these classes is an implementation detail
- deprecated BROWSER_PROVIDERS was removed completely
- `@angular/compiler` was removed from the ts-api-guardian check since this package shouldn't contain anything that users need to directly import
- the rest of the api surface was conservatively marked as stable or experimental

BREAKING CHANGES: DomEventsPlugin and KeyEventsPlugin previously exported from core are no longer public - these classes are implementation detail.

Previously deprecated BROWSER_PROVIDERS was completely removed from platform-browser.

Closes #9236
Closes #9235
Ref #9234

modules/@angular/platform-browser/src/security/dom_sanitization_service.ts

@@ -19,17 +19,44 @@ export {SecurityContext};
 
 /**
  * Marker interface for a value that's safe to use in a particular context.
+ *
+ * @stable
  */
 export interface SafeValue {}
-/** Marker interface for a value that's safe to use as HTML. */
+
+/**
+ * Marker interface for a value that's safe to use as HTML.
+ *
+ * @stable
+ */
 export interface SafeHtml extends SafeValue {}
-/** Marker interface for a value that's safe to use as style (CSS). */
+
+/**
+ * Marker interface for a value that's safe to use as style (CSS).
+ *
+ * @stable
+ */
 export interface SafeStyle extends SafeValue {}
-/** Marker interface for a value that's safe to use as JavaScript. */
+
+/**
+ * Marker interface for a value that's safe to use as JavaScript.
+ *
+ * @stable
+ */
 export interface SafeScript extends SafeValue {}
-/** Marker interface for a value that's safe to use as a URL linking to a document. */
+
+/**
+ * Marker interface for a value that's safe to use as a URL linking to a document.
+ *
+ * @stable
+ */
 export interface SafeUrl extends SafeValue {}
-/** Marker interface for a value that's safe to use as a URL to load executable code from. */
+
+/**
+ * Marker interface for a value that's safe to use as a URL to load executable code from.
+ *
+ * @stable
+ */
 export interface SafeResourceUrl extends SafeValue {}
 
 /**
@@ -55,6 +82,8 @@ export interface SafeResourceUrl extends SafeValue {}
  * It is not required (and not recommended) to bypass security if the value is safe, e.g. a URL that
  * does not start with a suspicious protocol, or an HTML snippet that does not contain dangerous
  * code. The sanitizer leaves safe values intact.
+ *
+ * @stable
  */
 export abstract class DomSanitizationService implements SanitizationService {
   /**