Summary

• Adds a client-only signal?: AbortSignal option next to every existing timeout option on action, getter and navigation methods.
• Aborting cancels the in-flight server call via a __cancel__ wire message that aborts the dispatcher's ProgressController; a pre-aborted signal throws signal.reason synchronously.
• Internally, the signal travels as a required second argument on every client channel method, mirroring how progress works on the dispatcher side. That way the compiler enforces we forward it everywhere, rather than letting it hide in a params field.
• Follows up feat: add AbortSignal support to client-side Waiter methods #41136 (Waiter-based waitFor* methods), which is excluded here as it already has signal support.

Not included (follow-ups)

• expect assertions (toBeVisible, etc.) — deferred to a separate PR.
• ElementHandle.inputValue — intentionally left out. Unlike Locator/Page/Frame.inputValue (which route through the Frame.inputValue protocol method that carries timeout), the ElementHandle.inputValue protocol method (packages/protocol/spec/handles.yml) declares no parameters, so the timeout option the public types have long advertised there is silently dropped by the wire validator. Adding signal would require a signature change and inherit that broken-timeout behavior. Fixing it is a separate change: add timeout/signal to the inputValue entry in handles.yml.

Refs #40578