The functions that take a TIntermSequence always copy out / Swap the
contents away.  This change makes all TIntermSequences live on the stack
instead of being newed.

Bug: angleproject:5535
Change-Id: I942f1c5e57b00199d5308183f71bd9e18b0608bd
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2636679Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Tim Van Patten <timvp@google.com>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>