This is a reland of commit 51b99213

Fixed in reland:
- bytecode_age was incorrectly still accessed as an int8 (instead
  of int16).
- age and osr state were incorrectly reset on ia32 (16-bit write
  instead of 32-bit).

Original change's description:
> [osr] Add an install-by-offset mechanism
>
> .. for concurrent OSR. There, the challenge is to hit the correct
> JumpLoop bytecode once compilation completes, since execution has
> moved on in the meantime.
>
> This CL adds a new mechanism to request installation at a specific
> bytecode offset. We add a new `osr_install_target` field to the
> BytecodeArray:
>
>   bitfield struct OSRUrgencyAndInstallTarget extends uint16 {
>     osr_urgency: uint32: 3 bit;
>     osr_install_target: uint32: 13 bit;
>   }
>
>   // [...]
>   osr_urgency_and_install_target: OSRUrgencyAndInstallTarget;
>   bytecode_age: uint16;  // Only 3 bits used.
>   // [...]
>
> Note urgency and install target are packed into one 16 bit field,
> we can thus merge both checks into one comparison within JumpLoop.
> Note also that these fields are adjacent to the bytecode age; we
> still reset both OSR state and age with a single (now 32-bit)
> store.
>
> The install target is the lowest 13 bits of the bytecode offset.
> When set, every reached JumpLoop will check `is this my offset?`,
> and if yes, jump into runtime to tier up.
>
> Drive-by: Rename BaselineAssembler::LoadByteField to LoadWord8Field.
>
> Bug: v8:12161
> Change-Id: I275d468b19df3a4816392a2fec0713a8d211ef80
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3571812
> Reviewed-by: Leszek Swirski <leszeks@chromium.org>
> Commit-Queue: Jakob Linke <jgruber@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#79853}

Bug: v8:12161
Change-Id: I7c59b2a2aacb1d7d40fdf39396ec9d8d48b0b9ac
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3578543Reviewed-by: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Jakob Linke <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79911}