On x86-64, we spend significant time constructing and copying operands
in Liftoff (around 5% locally). Inlining the constructor and helper
functions removes most of the overhead.

R=clemensb@chromium.org

Bug: v8:10576
Change-Id: I1663e3e92abe7683eba9320e77fce9be8f84b4ca
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2225023
Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68130}