Reland "[discard] Ensures FrameNodes transition lifecycle state correctly"

This is a reland of commit 758f6c0a6405fb473d2e42e4dd55dd9a44986c50

Initialized page_lifecycle_state_ (see diff against PS1).

Original change's description:
> [discard] Ensures FrameNodes transition lifecycle state correctly
>
> The current implementation of web-contents retaining tab discard
> can result in invalid lifecycle state transitions for frozen tabs.
>
> Consider the following event flow:
>   1. A tab is frozen
>   2. The same tab is then discarded
>   3. The page lifecycle state is synchronously updated to DISCARDED
>      in TabLifecycleUnit::FinishDiscardAndPreserveWebContents()
>   4. The synchronous shutdown of the RenderProcessHost causes a
>      FrameNodeObserver::OnFrameNodeRemoved() event to be queued
>      on the performance manager graph thread
>   5. This changes the balance of frozen frames and the frame tree
>      is interpreted as ACTIVE
>        This queues a update-lifecycle-state ACTIVE event on the
>        main thread
>   6. On the main thread a state transition from DISCARDED to ACTIVE
>      is attempted (which is invalid, the tab is still discarded)
>
> This results in the tab being set to an invalid page lifecycle
> state. Consequently further discards may be attempted on the tab
> given it is flagged ACTIVE, however these will either fail or no-op
> as the tab is actually discarded.
>
> This CL addresses this issue by updating the TabLifecycleUnit to
> independently keep track of:
>   - if the WebContents is discarded in `is_discarded_`
>   - the page's LifecycleState in `page_lifecycle_state_`
>       this is either kActive or kFrozen (kDiscarded is removed)
>
> The LifecycleUnitState is the computed based on the above. This is
> done since it is possible to end up with a discarded page who's
> lifecycle state is either kActive or kFrozen.
>
> Bug: 394242157
> Change-Id: I42517404b90ddd593c57e12b8bf48b4433e3227a
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6229171
> Reviewed-by: Sam McNally <sammc@chromium.org>
> Reviewed-by: Francois Pierre Doray <fdoray@chromium.org>
> Commit-Queue: Thomas Lukaszewicz <tluk@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1417926}

Bug: 394242157
Change-Id: Ia02ef7345691c60ed2019caecd27689ebca3b87a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6248477
Reviewed-by: Francois Pierre Doray <fdoray@chromium.org>
Reviewed-by: Sam McNally <sammc@chromium.org>
Commit-Queue: Thomas Lukaszewicz <tluk@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1418326}