docs: consolidate theming guides (#29988)

Co-authored-by: Andrew Seguin <[email protected]>
(cherry picked from commit 02d703b)

Author: andrewseguin

CHANGELOG_ARCHIVE.md

@@ -7297,7 +7297,7 @@ contains all of the components. Build tools such as [`rollup.js`](http://rollupj
 tree-shaking to eliminate the code for components that you aren't using.
 
 The addition of theming as also changed the directory structure for bringing the core css into your
-application. See the new [theming guide](guides/theming.md) for more information.
+application. See the new [theming guide](guides/theming-with-config) for more information.
 
 
 ### Features

guides/customizing-component-styles.md

@@ -26,7 +26,7 @@ The Angular Material `ng add` schematic helps you set up an Angular CLI project
 
 - Ensure [project dependencies](./getting-started#step-1-install-angular-material-angular-cdk-and-angular-animations) are placed in `package.json`
 - Enable the [BrowserAnimationsModule](./getting-started#step-2-configure-animations) in your app module
-- Add either a [prebuilt theme](./theming#pre-built-themes) or a [custom theme](./theming#defining-a-custom-theme)
+- Add either a prebuilt theme or a custom theme
 - Add Roboto fonts to your `index.html`
 - Add the [Material Icon font](./getting-started#step-6-optional-add-material-icons) to your `index.html`
 - Add global styles to