This change makes the SFI to bytecode link pseudo-weak. The marking visitors
check whether the bytecode is old, and if so, don't mark it and instead
push the SFI onto a bytecode_flushing_candidates worklist. Once marking
is complete, this list is walked, and for any of the candidates who's bytecode
has not been marked (i.e., is only referenced by the shared function info),
the bytecode is flushed and the SFI has the function data replaced with
an UncompiledData (which overwrites the flushed bytecode array).

Since we don't track JSFunctions, these can still think the underlying
function is compiled, and so calling them will invoke
InterpreterEntryTrampoline. As such, logic is added to
InterpreterEntryTrampoline to detect flushed functions, and enter
CompileLazy instead.

BUG=v8:8395

Change-Id: I4afba79f814ca9a92dec45d59485935845a6669d
Reviewed-on: https://chromium-review.googlesource.com/c/1348433
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58158}