docs: use viewChild signal queries and modern patterns in code examples

[yogeshwaran-c]

What kind of change does this PR introduce?

Documentation update.

What is the current behavior?

Several documentation files use the decorator-based @ViewChild pattern in
code examples, along with @NgModule providers and constructor injection.
These patterns are outdated since Angular v17+ introduced signal-based queries
and standalone components became the default.

Relates to #32709

What is the new behavior?

• Replace @ViewChild with viewChild.required() signal queries
• Replace @ViewChildren prose references with viewChildren
• Replace @NgModule provider blocks with bootstrapApplication
• Replace constructor injection with inject()
• Replace AfterViewInit lifecycle with afterNextRender

Files changed

File	Changes
src/cdk/a11y/a11y.md	@ViewChildren -> viewChildren in prose
src/google-maps/google-map/README.md	Remove ViewChild decorator reference from prose
src/google-maps/map-info-window/README.md	@ViewChild -> viewChild.required() in example
src/material/core/ripple/ripple.md	@ViewChild -> viewChild.required(), @NgModule -> bootstrapApplication, constructor -> inject()
src/material/datepicker/datepicker.md	@ViewChild -> viewChild.required() with generic type
src/material/menu/menu.md	@ViewChild -> viewChild.required() in example
src/material/sidenav/sidenav.md	@ViewChild -> viewChild.required(), AfterViewInit -> afterNextRender

Additional context

All signal query calls use viewChild.required() since the queried elements are
expected to always exist in the template. Signal queries return a Signal<T>, so
the call-site invocation syntax changes from this.foo.method() to
this.foo().method().