Since the new Objects were introduced, we can no longer cast integers to
and Object pointer and call methods on them in gdb (due to how gdb's
expression evaluator deals with temporaries). So, we add a new helper
method to our gdbinit, "$job", which takes an address and returns an
Object that is now exists in real (stack) memory.

Bug: v8:8994
Change-Id: I760a007e7d2303e3a4b1fecb87e094fb9974e91e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1523329
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60245}