When disassembling code (in particular embedded builtins), try to
print better information about root-relative accesses. For example:

 REX.W movq rdx,[r13+0x548]
 REX.W movq rax,[r13+0x10a8]

turns into

 REX.W movq rdx,[r13+0x548] (root (0x1ff420d0ccd9 <FixedArray[1672]>))
 REX.W movq rax,[r13+0x10a8] (external reference (check_object_type))

This is a band-aid solution until we come up with something better. It
does not understand multi-instruction sequences (such as loads from
the builtins constants table), assumes every kRootRegister-relative
access is actually root-relative (i.e. the register is not initialized
to some other value), and is limited to a particular instruction
pattern.

Bug: v8:6666,v8:7969
Change-Id: I35af92e8233c9bb0f2ad6ba0e86bd0ab69177205
Reviewed-on: https://chromium-review.googlesource.com/1146806
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54777}