Remove the BaselineData intermediate structure for baseline code, and
write the baseline Code object into the SharedFunctionInfo directly. We
still need a pointer to the BytecodeArray/InterpreterData, so re-use the
Code object's deoptimization data slot for this (baseline code doesn't
have deoptimization data).

A consequence of this is that the BytecodeArray pointer becomes
immutable when there is baseline code. This means that we cannot install
a debug BytecodeArray while baseline code is active (we have to flush it
first), and we can't tier-up code with debug BytecodeArray to baseline.

Change-Id: I53b93ec4d4c64b833603d7992f246982fcd97596
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3118548
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/main@{#76675}