The {code_table_} only contains entries for the declared functions, and
is indexed by a slot index. The {PatchJumpTableLocked} and
{PatchJumpTablesLocked} functions on the other hand expected a function
index (offset by the number of imported functions). From that it
computes the slot index again.
This translation was missing in one place. This CL fixes this by
directly passing the slot index instead of the function index to these
methods. In all locations, we computed the slot index anyway for
addressing the code table.

Drive-by: Use more unique_ptr for managing the {code_table_}. This
avoids ever having to store raw pointers.

R=ahaas@chromium.org

Bug: v8:9477
Change-Id: I81caa53b74da010aee5854879e98e82b7773098b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1813742
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63896}