fix: consistently rewrite Injector to INJECTOR (#23008)

In Ivy mode we rewrite references to Injector to INJECTOR in ngInjectableDef, to fix tree-shaking.

This changes the rewrite to happen always, even in non-Ivy mode, and makes Angular understand
INJECTOR across the board at runtime.

PR Close #23008

packages/compiler/src/injectable_compiler.ts

@@ -63,7 +63,7 @@ export class InjectableCompiler {
       let tokenExpr: o.Expression;
       if (typeof token === 'string') {
         tokenExpr = o.literal(token);
-      } else if (token === this.tokenInjector && this.alwaysGenerateDef) {
+      } else if (token === this.tokenInjector) {
         tokenExpr = o.importExpr(Identifiers.INJECTOR);
       } else {
         tokenExpr = ctx.importExpr(token);