build(bazel): Turning on strictPropertyInitialization for Angular. (#24572)

All errors for existing fields have been detected and suppressed with a
`!` assertion.

Issue/24571 is tracking proper clean up of those instances.

One-line change required in ivy/compilation.ts, because it appears that
the new syntax causes tsickle emitted node to no longer track their
original sourceFiles.

PR Close #24572

packages/compiler/src/css_parser/css_lexer.ts

@@ -116,7 +116,8 @@ function _trackWhitespace(mode: CssLexerMode) {
 }
 
 export class CssScanner {
-  peek: number;
+  // TODO(issue/24571): remove '!'.
+  peek !: number;
   peekPeek: number;
   length: number = 0;
   index: number = -1;